Vasyl Yurchyshyn | NJIT - Academia.edu (original) (raw)

Vasyl Yurchyshyn

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Papers by Vasyl Yurchyshyn

Advances in Geosciences - A 6-Volume Set, 2010

The Astrophysical Journal, 2002

The Astrophysical Journal, 2008

The Astrophysical Journal, 2015

Space Weather, 2004

We studied the relationship between the projected speed of coronal mass ejections (CMEs), determi... more We studied the relationship between the projected speed of coronal mass ejections (CMEs), determined from a sequence of Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph Experiment (SOHO/LASCO) images, and the hourly averaged magnitude of the Bz component of the magnetic field in an interplanetary ejecta, as measured by the Advanced Composition Explorer (ACE) magnetometer in the Geocentric Solar Magnetospheric Coordinate System (GSM). For CMEs that originate at the central part of the solar disk we found that the intensity of Bz is correlated with the projected speed of the CME, Vp. The relationship is more pronounced for very fast ejecta (Vp > 1200 km/s), while slower events display larger scatter. We also present data which support earlier conclusions about the correlation of Bz and the Dst index of geomagnetic activity. A possible application of the results to space weather forecasting is discussed.

$Research paper thumbnail of Intermittency and multifractality spectra of the magnetic field in solar active regions$

Using high resolution off-band \ha\ data from the New Solar Telescope and Morlet wavelet analysis... more Using high resolution off-band \ha\ data from the New Solar Telescope and Morlet wavelet analysis technique, we analyzed transverse motions of type II spicules observed near the North Pole of the Sun. Our new findings are that i) some of the observed type II spicules display kink or an inverse "Y" features, suggesting that their origin may be due to magnetic reconnection, and ii) type II spicules tend to display coherent transverse motions/oscillations. Also, the wavelet analysis detected significant presence of high frequency oscillations in type II spicules, ranging from 30 to 180 s with the the average period of 90 s. We conclude that at least some of type II spicules and their coherent transverse motions may be caused by reconnection between large scale fields rooted in the intergranular lanes and and small-scale emerging dipoles, a process that is know to generate high frequency kink mode MHD waves propagating along the magnetic field lines.

The Astrophysical Journal, 2010

The Astrophysical Journal, 2009

Solar Physics - SOL PHYS, 2002

We report on a prominence eruption as seen in Halpha with the Crimean Lyot coronagraph, the globa... more We report on a prominence eruption as seen in Halpha with the Crimean Lyot coronagraph, the global Halpha network, and coronal images from the LASCO C2 instrument on board SOHO. We observed an Halpha eruption at the northwest solar limb between 07:38:50 UT and 07:58:29 UT on 11 August 2000. The eruption originated in a quiet-Sun region and was not associated with an Halpha filament. No flare was associated with the eruption, which may indicate that, in this case, a flux rope was formed prior to the eruption of the magnetic field. The Halpha images and an Halpha Dopplergram show a helical structure present in the erupted magnetic field. We suggest that the driving mechanism of the eruption may be magnetic flux emergence or magnetic flux injection. The limb Halpha observations provide missing data on CME speed and acceleration in the lower corona. Our data show that the prominence accelerated impulsively at 5.5 km s-2 and reached a speed slightly greater than 800 km s-1 in a narrow re...