L. Golub - Academia.edu (original) (raw)
Papers by L. Golub
Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. T... more Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause activity and the response occur on large spatial scales. Thus both high resolution and large fields of view are needed. Observations from SMM, Yohkoh,
The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35... more The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. XRT, designed for full sun imaging over the wavelength 6-60 Angstroms, will be the highest resolution solar X-Ray telescope ever flown. Images will be recorded by a 2048 X 2048 back-illuminated CCD with 13.5 mum pixels (1
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010
We present the design for a stigmatic grazing incidence X-ray spectrograph designed for solar cor... more We present the design for a stigmatic grazing incidence X-ray spectrograph designed for solar coronal observations. The spectrograph is composed of a slit, a pair of paraboloid mirrors and a plano varied-line-space grating. All reflective surfaces of the spectrograph operate at an angle of incidence of 88 degrees, and covers a wavelength range of 0.6 to 2.4nm (0.5 to 2.0keV). The design achieves 1.5pm spectral resolution and 15 mum spatial resolution over a 2.5mmlong slit. The current spectrograph design is intended for a sounding rocket experiment, and designed to fit inside a NASA sounding rocket payload behind a 1.1m focal length Wolter Type-1 telescope. This combination will have a 2.5arcsec spatial resolution and a 8 arcminute slit length. We are currently fabricating a laboratory prototype of the spectrograph to demonstrate the performance and establish the alignment procedures for a flight model.
The Atmospheric Imaging Assembly (AIA) will be one of the instruments on the Solar Dynamics Obser... more The Atmospheric Imaging Assembly (AIA) will be one of the instruments on the Solar Dynamics Observatory (SDO). It will image the solar transition region and corona in multiple EUV and UV wavelengths simultaneously, using four aligned telescopes. Hence, AIA will be capable of high-cadence, spatially resolved temperature discrimination of solar plasmas. We discuss the design of AIA, with focus on its ability for temperature diagnostics. We consider different methods for reconstruction of differential emission measures, since this will be one of the more important data products. This work is supported under contract SP02D4301R to the Lockheed Martin Corp.
The Astrophysical Journal, 1995
The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of high-resolution full-disk so... more The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of high-resolution full-disk solar images which were exposed simultaneously by X-rays in a passband at 63.5 Å and by visible light. The perfect alignment of a photospheric visible-light image with a coronal X-ray image enables us to present observations of X-ray intensity as a function of an accurately determined height
Science, 2007
The Sun continuously expels a huge amount of ionized material into interplanetary space as the so... more The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray–emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to ∼1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.
A broad description of the Skylab X-ray telescope experiment is given. The design and development... more A broad description of the Skylab X-ray telescope experiment is given. The design and development of the S-054 X-ray telescope and the X-ray imaging system are reviewed, and the primary telescope is described along with its spectral characteristics, imaging optics, camera, and film. The technique for determining the temperature and emission integral of the coronal plasma from X-ray photographs is
Lecture Notes in Physics
ABSTRACT
We have applied a Magnetic Charge Topology model to investigate what changes in the properties of... more We have applied a Magnetic Charge Topology model to investigate what changes in the properties of the magnetic field are responsible for different coronal emission behavior of the coronal loops in two different active regions. Observations from the X-ray Telescope (XRT) on board Hinode and the Transition Region and Coronal Expolorer (TRACE) were used, along with time-series of magnetograms for
The Hi-C sounding rocket data can be used to determine the rate and approximate magnitude of free... more The Hi-C sounding rocket data can be used to determine the rate and approximate magnitude of free energy released by the active region coronal magnetic field. We present the results from the analysis of two regions within the Hi-C field-of-view. Hi-C data is also used to determine the temperature and density of structures and we offer conclusions on the spatial scale for these features.
We present X-ray imaging observations with Hinode X-Ray Telescope (XRT) of an active region NOAA ... more We present X-ray imaging observations with Hinode X-Ray Telescope (XRT) of an active region NOAA AR 10942 made in the period of 20-22 February 2007. A prominent feature that drew our particular attention is that there revealed continuous upflow of soft-X-ray-emitting plasmas along apparently-open field lines towards the outer corona emanating from the edge of the active region. The field
The Astrophysical Journal, 1982
Detection of quiescent X-ray emission from the stellar components of the Alpha Cen system: Alpha ... more Detection of quiescent X-ray emission from the stellar components of the Alpha Cen system: Alpha Cen A (G2 V) and Alpha Cen B (K1 V) is reported. Contrary to previous theoretical expectations, both stars are found to be X-ray emitters and at about the same level: Lx = 1.2 x 10 to the 27th and 2.8 x 10 to the
![Research paper thumbnail of Apparent Flows above an Active Region Observed with the [ITAL]Transition Region and Coronal Explorer[/ITAL]](https://attachments.academia-assets.com/105396243/thumbnails/1.jpg)
](The Astrophysical Journal, 2001
brightness variations along a dense bundle of coronal field lines in the southwest corner of the ... more brightness variations along a dense bundle of coronal field lines in the southwest corner of the active region were observed. Movies made of this region give the impression of continuous intermittent outflow in this bundle of coronal loops; such apparent outflow is often seen in the TRACE data. In this Letter, we present an analysis of four separate flow events occurring in three different loops. These events are used as tracers of the flow in order to characterize its physical properties, such as apparent velocity. The projected velocities of the intensity fronts of these flows (and hence lower limits of true velocities) are between 5 and 20 km s Ϫ1. Comparisons of the observed intensities with those predicted by a quasi-static model suggest that the events can be explained only by a mass flow from the chromosphere into the corona. The persistence of the flows, and their ubiquity in the TRACE observations, indicates that hydrostatic loops models are not applicable to this class of coronal structures.
The Astrophysical Journal, 1991
The Astrophysical Journal, 1981
The Astrophysical Journal, 2000
![Research paper thumbnail of [ITAL]TRACE[/ITAL] and [ITAL]Yohkoh[/ITAL] Observations of High-Temperature Plasma in a Two-Ribbon Limb Flare](https://attachments.academia-assets.com/105396251/thumbnails/1.jpg)
](The Astrophysical Journal, 1999
The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wi... more The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (-10 7 K) at high spatial resolution (0Љ .5 pixels) makes it a unique instrument for observing 4
The Astrophysical Journal, 2010
ABSTRACT Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistica... more ABSTRACT Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistical study of coronal mass ejections (CMEs) with and without distinct low coronal signatures (LCSs) from 2009 January 1 to August 31. During this period, the lines of sight from STEREO A and B are almost perpendicular and nearly a quarter of the Sun was observed by both. We identified 34 CMEs that originated from around this area and find that (1) about 1 out of 3 CMEs that were studied during 8 months of solar minimum activity are stealth CMEs; a CME is stealth if no distinct LCS (such as coronal dimming, coronal wave, filament eruption, flare, post-eruptive arcade) can be found on the disk. (2) The speeds of the stealth CMEs without LCSs are typically below 300 km s–1. Comparing with the slow CMEs with LCSs, the stealth CMEs did not show any clear differences in their velocity and acceleration evolution. (3) The source regions of the stealth CMEs are usually located in the quiet Sun rather than active regions. Detailed study indicates that more than half of the stealth CMEs in this paper showed some faint change of the coronal structures (likely parts of flux ropes) when they could be observed over the solar limb before or during the CME evolution. Finally, we note that space weather detection systems based on LCSs totally independent of coronagraph data may fail to detect a significant proportion of CMEs.
Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. T... more Hot magnetized plasmas - typified by the solar corona - are ubiquitous throughout the universe. The physics governing the dynamics of such plasmas takes place on remarkably small spatial and temporal scales, while both the cause activity and the response occur on large spatial scales. Thus both high resolution and large fields of view are needed. Observations from SMM, Yohkoh,
The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35... more The Solar-B X-ray telescope (XRT) is a grazing-incidence modified Wolter I X-ray telescope, of 35 cm inner diameter and 2.7 m focal length. XRT, designed for full sun imaging over the wavelength 6-60 Angstroms, will be the highest resolution solar X-Ray telescope ever flown. Images will be recorded by a 2048 X 2048 back-illuminated CCD with 13.5 mum pixels (1
Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 2010
We present the design for a stigmatic grazing incidence X-ray spectrograph designed for solar cor... more We present the design for a stigmatic grazing incidence X-ray spectrograph designed for solar coronal observations. The spectrograph is composed of a slit, a pair of paraboloid mirrors and a plano varied-line-space grating. All reflective surfaces of the spectrograph operate at an angle of incidence of 88 degrees, and covers a wavelength range of 0.6 to 2.4nm (0.5 to 2.0keV). The design achieves 1.5pm spectral resolution and 15 mum spatial resolution over a 2.5mmlong slit. The current spectrograph design is intended for a sounding rocket experiment, and designed to fit inside a NASA sounding rocket payload behind a 1.1m focal length Wolter Type-1 telescope. This combination will have a 2.5arcsec spatial resolution and a 8 arcminute slit length. We are currently fabricating a laboratory prototype of the spectrograph to demonstrate the performance and establish the alignment procedures for a flight model.
The Atmospheric Imaging Assembly (AIA) will be one of the instruments on the Solar Dynamics Obser... more The Atmospheric Imaging Assembly (AIA) will be one of the instruments on the Solar Dynamics Observatory (SDO). It will image the solar transition region and corona in multiple EUV and UV wavelengths simultaneously, using four aligned telescopes. Hence, AIA will be capable of high-cadence, spatially resolved temperature discrimination of solar plasmas. We discuss the design of AIA, with focus on its ability for temperature diagnostics. We consider different methods for reconstruction of differential emission measures, since this will be one of the more important data products. This work is supported under contract SP02D4301R to the Lockheed Martin Corp.
The Astrophysical Journal, 1995
The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of high-resolution full-disk so... more The Normal Incidence X-Ray Telescope (NIXT) obtained a unique set of high-resolution full-disk solar images which were exposed simultaneously by X-rays in a passband at 63.5 Å and by visible light. The perfect alignment of a photospheric visible-light image with a coronal X-ray image enables us to present observations of X-ray intensity as a function of an accurately determined height
Science, 2007
The Sun continuously expels a huge amount of ionized material into interplanetary space as the so... more The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray–emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to ∼1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun.
A broad description of the Skylab X-ray telescope experiment is given. The design and development... more A broad description of the Skylab X-ray telescope experiment is given. The design and development of the S-054 X-ray telescope and the X-ray imaging system are reviewed, and the primary telescope is described along with its spectral characteristics, imaging optics, camera, and film. The technique for determining the temperature and emission integral of the coronal plasma from X-ray photographs is
Lecture Notes in Physics
ABSTRACT
We have applied a Magnetic Charge Topology model to investigate what changes in the properties of... more We have applied a Magnetic Charge Topology model to investigate what changes in the properties of the magnetic field are responsible for different coronal emission behavior of the coronal loops in two different active regions. Observations from the X-ray Telescope (XRT) on board Hinode and the Transition Region and Coronal Expolorer (TRACE) were used, along with time-series of magnetograms for
The Hi-C sounding rocket data can be used to determine the rate and approximate magnitude of free... more The Hi-C sounding rocket data can be used to determine the rate and approximate magnitude of free energy released by the active region coronal magnetic field. We present the results from the analysis of two regions within the Hi-C field-of-view. Hi-C data is also used to determine the temperature and density of structures and we offer conclusions on the spatial scale for these features.
We present X-ray imaging observations with Hinode X-Ray Telescope (XRT) of an active region NOAA ... more We present X-ray imaging observations with Hinode X-Ray Telescope (XRT) of an active region NOAA AR 10942 made in the period of 20-22 February 2007. A prominent feature that drew our particular attention is that there revealed continuous upflow of soft-X-ray-emitting plasmas along apparently-open field lines towards the outer corona emanating from the edge of the active region. The field
The Astrophysical Journal, 1982
Detection of quiescent X-ray emission from the stellar components of the Alpha Cen system: Alpha ... more Detection of quiescent X-ray emission from the stellar components of the Alpha Cen system: Alpha Cen A (G2 V) and Alpha Cen B (K1 V) is reported. Contrary to previous theoretical expectations, both stars are found to be X-ray emitters and at about the same level: Lx = 1.2 x 10 to the 27th and 2.8 x 10 to the
The Astrophysical Journal, 2001
brightness variations along a dense bundle of coronal field lines in the southwest corner of the ... more brightness variations along a dense bundle of coronal field lines in the southwest corner of the active region were observed. Movies made of this region give the impression of continuous intermittent outflow in this bundle of coronal loops; such apparent outflow is often seen in the TRACE data. In this Letter, we present an analysis of four separate flow events occurring in three different loops. These events are used as tracers of the flow in order to characterize its physical properties, such as apparent velocity. The projected velocities of the intensity fronts of these flows (and hence lower limits of true velocities) are between 5 and 20 km s Ϫ1. Comparisons of the observed intensities with those predicted by a quasi-static model suggest that the events can be explained only by a mass flow from the chromosphere into the corona. The persistence of the flows, and their ubiquity in the TRACE observations, indicates that hydrostatic loops models are not applicable to this class of coronal structures.
The Astrophysical Journal, 1991
The Astrophysical Journal, 1981
The Astrophysical Journal, 2000
The Astrophysical Journal, 1999
The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wi... more The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (-10 7 K) at high spatial resolution (0Љ .5 pixels) makes it a unique instrument for observing 4
The Astrophysical Journal, 2010
ABSTRACT Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistica... more ABSTRACT Taking advantage of the two viewpoints of the STEREO spacecraft, we present a statistical study of coronal mass ejections (CMEs) with and without distinct low coronal signatures (LCSs) from 2009 January 1 to August 31. During this period, the lines of sight from STEREO A and B are almost perpendicular and nearly a quarter of the Sun was observed by both. We identified 34 CMEs that originated from around this area and find that (1) about 1 out of 3 CMEs that were studied during 8 months of solar minimum activity are stealth CMEs; a CME is stealth if no distinct LCS (such as coronal dimming, coronal wave, filament eruption, flare, post-eruptive arcade) can be found on the disk. (2) The speeds of the stealth CMEs without LCSs are typically below 300 km s–1. Comparing with the slow CMEs with LCSs, the stealth CMEs did not show any clear differences in their velocity and acceleration evolution. (3) The source regions of the stealth CMEs are usually located in the quiet Sun rather than active regions. Detailed study indicates that more than half of the stealth CMEs in this paper showed some faint change of the coronal structures (likely parts of flux ropes) when they could be observed over the solar limb before or during the CME evolution. Finally, we note that space weather detection systems based on LCSs totally independent of coronagraph data may fail to detect a significant proportion of CMEs.