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Papers by Jose Luis Hormaechea

arXiv (Cornell University), Feb 25, 2021

We present observations of the sudden outburst of the α Carinid meteor shower recorded with the S... more We present observations of the sudden outburst of the α Carinid meteor shower recorded with the Southern Argentina Agile MEteor Radar-Orbital System (SAAMER-OS) near the South Toroidal sporadic region. The outburst peaked between 21 UT and 22 UT on October 14, 2020 and lasted 7 days (199 • ≤ λ ≤ 205 •) with a mean Sun-centered geocentric ecliptic radiant of λ g − λ = 271 • .04, β g = −76 • .4, and a geocentric speed of 33.3 km s −1. Assuming a mass index value of s = 2.0, we compute a peak 24 hour-average flux of 0.029 met. km −2 hr −1 to a limit of 9th magnitude, which is equivalent to a zenithal hourly rate (ZHR) of 5.7, and comparable to other established showers with similar mass indices. By further estimating the peak fluxes for other typical mass index values, we find that the outburst likely never exceeded a maximum ZHR of ∼ 44, well below the activity of other strong showers. The mean orbital elements resemble those of a short-period object: a = 3.5 ± 0.1 au, q 1 au, e = 0.72 ± 0.02, i = 55 • .8 ± 0 • .3, ω = 1 • ± 173 • , Ω = 21 • .7, and are similar to those derived for two previous shower outbursts observed with SAAMER-OS at high southern ecliptic latitudes. Using the D criterion did not reveal a parent object associated with this shower in the known object catalogues.

The Astronomical Journal, May 23, 2019

We present determinations of the meteoroid differential mass-index, s, using over a decade of met... more We present determinations of the meteoroid differential mass-index, s, using over a decade of meteor observations from the Southern Argentina Agile MEteor Radar (SAAMER). For this, we employ an autonomous statistical technique to determine this parameter from the measured radar echo amplitudes. Unlike previous studies, we examine the role of the system noise in the determination of this parameter and found that if not taking into account appropriately, the results can yield significant over-estimations of the mass-index. In general, we found that a value of s = 2.0 represents SAAMER's results in general agreement with recent studies performed in the northern hemisphere. We explore both, the index interannual and seasonal variability and, unlike previous studies, we found it to be constant, except during the presence of the Southern delta Aquariids meteor shower which is so strong that dominates the meteor counts when present. Our study suggests that using the maximum echo amplitude for these studies is not ideal as it can be biased by many factors which make the inaccuracies larger than the precision estimated by the fitting routine. A method that results in a more direct estimate of the electron line density would be required which takes into account range, gain pattern, system noise, etc.

Journal Of Geophysical Research: Space Physics, Mar 1, 2014

• Routine detection of meteor head echoes using a meteor radar • A new technique to perform conti... more • Routine detection of meteor head echoes using a meteor radar • A new technique to perform continuous and detail measurements of meteoroids • Link directly atmospheric processes with particle orbital characteristics

EGU General Assembly Conference Abstracts, Apr 1, 2017

Geodetic GNSS observations at 43 sites well distributed over the Southern Patagonian Icefield reg... more Geodetic GNSS observations at 43 sites well distributed over the Southern Patagonian Icefield region yield site velocities with a mean accuracy of 1 mm/a and 6 mm/a for the horizontal and vertical components, respectively. These velocities are analyzed to reveal the magnitudes and patterns of vertical and horizontal present-day crustal deformation as well as their primary driving processes. The observed vertical velocities confirm a rapid uplift, with rates peaking at 41 mm/a, causally related to glacial-isostatic adjustment (GIA). They yield now an unambiguous preference between two competing GIA models. Remaining discrepancies between the preferred model and our observations point toward an effective upper mantle viscosity even lower than 1.6 • 10 18 Pa s and effects of lateral rheological heterogeneities. An analysis of the horizontal strain and strain-rate fields reveals some complex superposition, with compression dominating in the west and extension in the east. This deformation field suggests significant contributions from three processes: GIA, a western interseismic tectonic deformation field related to plate subduction, and an extensional strain-rate field related to active Patagonian slab window tectonics.

Scientific Reports, Sep 3, 2020

Gravity waves (GWs) are major contributors to middle and upper atmosphere dynamics because they a... more Gravity waves (GWs) are major contributors to middle and upper atmosphere dynamics because they account for large momentum and energy transports from sources at lower altitudes, and systematic and variable momentum and energy deposition where they dissipate. Mean seasonal GW momentum deposition closes the polar mesospheric jets, inducing a pole-to-pole residual circulation, and driving large-scale constituent transport and mean temperatures far from radiative equilibrium (Fritts & Alexander, 2003). GW energy dissipation accompanies breaking and leads to a range of instabilities, turbulence, and local heating and mixing. Their importance has been increasingly recognized over the past six decades, but many GW dynamics and effects have yet to be understood and quantified. GWs have many sources accompanying weather events in the troposphere and lower stratosphere. Of these, air flow over orography that generates mountain waves (MWs) yields the most significant local and statistical responses from the tropopause to the upper stratosphere based on global in situ and remote-sensing measurements (

ABSTRACT Time and Latitude results from the Rio Grande station since the starting of operation (M... more ABSTRACT Time and Latitude results from the Rio Grande station since the starting of operation (March 1979), are investigated. Internal and external precision are shown. Special attention is focused on apparent zenith distance variations, seasonal, personal and other effects. Observations consist of 700 groups (20000 transits).

Asteroids, Comets, Meteors 2014, Jul 1, 2014

The planetary science journal, Sep 20, 2021

We present an improved methodology to obtain absolute position and velocity of meteor head echoes... more We present an improved methodology to obtain absolute position and velocity of meteor head echoes, which can yield orbital information, generally limited to the use of High-Power, Large-Aperture radars, using an advanced-designed specular meteor radar. The observations, which were performed during a period when an outburst of the β-Taurid meteor shower was expected, were performed with the Southern Argentine Agile MEteor Radar. Three different methodologies are utilized to confirm our results: an improved interferometric solver building on previous work, and two different target localization techniques using remote receiving stations. In addition, we performed simultaneous optical observations during the meteor shower period. Overall, 71 radar head echo events were detected and analyzed using interferometry, while 12 of those events have detected signals strong enough to be analyzed using localization methods at the remote sites. Due to poor weather, however, the optical cameras only observed two events simultaneously with the radar. Results from these events are in agreement with the radar results. We find that interferometry methods from both radar and optical data resulted in the most accurate estimation of meteor properties, while target localization techniques derived similar results, albeit with larger uncertainty. We also computed heliocentric meteoroid orbits, and while a fraction was hyperbolic, we believe these to be due to uncertainty. Two events are suspected to be β-Taurid shower members.

Planetary and Space Science

arXiv (Cornell University), Feb 25, 2021

We present observations of the sudden outburst of the α Carinid meteor shower recorded with the S... more We present observations of the sudden outburst of the α Carinid meteor shower recorded with the Southern Argentina Agile MEteor Radar-Orbital System (SAAMER-OS) near the South Toroidal sporadic region. The outburst peaked between 21 UT and 22 UT on October 14, 2020 and lasted 7 days (199 • ≤ λ ≤ 205 •) with a mean Sun-centered geocentric ecliptic radiant of λ g − λ = 271 • .04, β g = −76 • .4, and a geocentric speed of 33.3 km s −1. Assuming a mass index value of s = 2.0, we compute a peak 24 hour-average flux of 0.029 met. km −2 hr −1 to a limit of 9th magnitude, which is equivalent to a zenithal hourly rate (ZHR) of 5.7, and comparable to other established showers with similar mass indices. By further estimating the peak fluxes for other typical mass index values, we find that the outburst likely never exceeded a maximum ZHR of ∼ 44, well below the activity of other strong showers. The mean orbital elements resemble those of a short-period object: a = 3.5 ± 0.1 au, q 1 au, e = 0.72 ± 0.02, i = 55 • .8 ± 0 • .3, ω = 1 • ± 173 • , Ω = 21 • .7, and are similar to those derived for two previous shower outbursts observed with SAAMER-OS at high southern ecliptic latitudes. Using the D criterion did not reveal a parent object associated with this shower in the known object catalogues.

The Astronomical Journal, May 23, 2019

We present determinations of the meteoroid differential mass-index, s, using over a decade of met... more We present determinations of the meteoroid differential mass-index, s, using over a decade of meteor observations from the Southern Argentina Agile MEteor Radar (SAAMER). For this, we employ an autonomous statistical technique to determine this parameter from the measured radar echo amplitudes. Unlike previous studies, we examine the role of the system noise in the determination of this parameter and found that if not taking into account appropriately, the results can yield significant over-estimations of the mass-index. In general, we found that a value of s = 2.0 represents SAAMER's results in general agreement with recent studies performed in the northern hemisphere. We explore both, the index interannual and seasonal variability and, unlike previous studies, we found it to be constant, except during the presence of the Southern delta Aquariids meteor shower which is so strong that dominates the meteor counts when present. Our study suggests that using the maximum echo amplitude for these studies is not ideal as it can be biased by many factors which make the inaccuracies larger than the precision estimated by the fitting routine. A method that results in a more direct estimate of the electron line density would be required which takes into account range, gain pattern, system noise, etc.

Journal Of Geophysical Research: Space Physics, Mar 1, 2014

• Routine detection of meteor head echoes using a meteor radar • A new technique to perform conti... more • Routine detection of meteor head echoes using a meteor radar • A new technique to perform continuous and detail measurements of meteoroids • Link directly atmospheric processes with particle orbital characteristics

EGU General Assembly Conference Abstracts, Apr 1, 2017

Geodetic GNSS observations at 43 sites well distributed over the Southern Patagonian Icefield reg... more Geodetic GNSS observations at 43 sites well distributed over the Southern Patagonian Icefield region yield site velocities with a mean accuracy of 1 mm/a and 6 mm/a for the horizontal and vertical components, respectively. These velocities are analyzed to reveal the magnitudes and patterns of vertical and horizontal present-day crustal deformation as well as their primary driving processes. The observed vertical velocities confirm a rapid uplift, with rates peaking at 41 mm/a, causally related to glacial-isostatic adjustment (GIA). They yield now an unambiguous preference between two competing GIA models. Remaining discrepancies between the preferred model and our observations point toward an effective upper mantle viscosity even lower than 1.6 • 10 18 Pa s and effects of lateral rheological heterogeneities. An analysis of the horizontal strain and strain-rate fields reveals some complex superposition, with compression dominating in the west and extension in the east. This deformation field suggests significant contributions from three processes: GIA, a western interseismic tectonic deformation field related to plate subduction, and an extensional strain-rate field related to active Patagonian slab window tectonics.

Scientific Reports, Sep 3, 2020

Gravity waves (GWs) are major contributors to middle and upper atmosphere dynamics because they a... more Gravity waves (GWs) are major contributors to middle and upper atmosphere dynamics because they account for large momentum and energy transports from sources at lower altitudes, and systematic and variable momentum and energy deposition where they dissipate. Mean seasonal GW momentum deposition closes the polar mesospheric jets, inducing a pole-to-pole residual circulation, and driving large-scale constituent transport and mean temperatures far from radiative equilibrium (Fritts & Alexander, 2003). GW energy dissipation accompanies breaking and leads to a range of instabilities, turbulence, and local heating and mixing. Their importance has been increasingly recognized over the past six decades, but many GW dynamics and effects have yet to be understood and quantified. GWs have many sources accompanying weather events in the troposphere and lower stratosphere. Of these, air flow over orography that generates mountain waves (MWs) yields the most significant local and statistical responses from the tropopause to the upper stratosphere based on global in situ and remote-sensing measurements (

ABSTRACT Time and Latitude results from the Rio Grande station since the starting of operation (M... more ABSTRACT Time and Latitude results from the Rio Grande station since the starting of operation (March 1979), are investigated. Internal and external precision are shown. Special attention is focused on apparent zenith distance variations, seasonal, personal and other effects. Observations consist of 700 groups (20000 transits).

Asteroids, Comets, Meteors 2014, Jul 1, 2014

The planetary science journal, Sep 20, 2021

We present an improved methodology to obtain absolute position and velocity of meteor head echoes... more We present an improved methodology to obtain absolute position and velocity of meteor head echoes, which can yield orbital information, generally limited to the use of High-Power, Large-Aperture radars, using an advanced-designed specular meteor radar. The observations, which were performed during a period when an outburst of the β-Taurid meteor shower was expected, were performed with the Southern Argentine Agile MEteor Radar. Three different methodologies are utilized to confirm our results: an improved interferometric solver building on previous work, and two different target localization techniques using remote receiving stations. In addition, we performed simultaneous optical observations during the meteor shower period. Overall, 71 radar head echo events were detected and analyzed using interferometry, while 12 of those events have detected signals strong enough to be analyzed using localization methods at the remote sites. Due to poor weather, however, the optical cameras only observed two events simultaneously with the radar. Results from these events are in agreement with the radar results. We find that interferometry methods from both radar and optical data resulted in the most accurate estimation of meteor properties, while target localization techniques derived similar results, albeit with larger uncertainty. We also computed heliocentric meteoroid orbits, and while a fraction was hyperbolic, we believe these to be due to uncertainty. Two events are suspected to be β-Taurid shower members.

Planetary and Space Science