solar flare

AAS Nova Features a Recent Publication by Philip Judge

kolinski — Thu, 18 Nov 2021 19:36:28 +0000

AAS Nova Features a Recent Publication by Philip Judge kolinski Thu, 11/18/2021 - 12:36

Author:

kolinski

Nov 18, 2021

Understanding the magnitude and occurrence of solar storms is key to predicting events that can be harmful to thousands of Earth-orbiting satellites and the welfare of astronauts. A recent paper by Philip Judge et al was highlighted in AAS Nova in a their featured article entitled, "A Better Space Weather Forecasting Tool."

Images to highlight the corrugated surfaces at which the centers of UV lines are formed (close to τ = 1) in MURaM calculations of the upper solar chromosphere. The calculations are from a numerical experiment where a magnetic flux system is emerging from beneath the solar atmosphere. The emergent fields carry with them plasma, which is revealed by the extended heights of the τ = 1 surfaces, which can exceed 10 Mm. Typically the Doppler line shifts in the lower transition region are smaller than the line widths (Athay & Dere 1991). Therefore the τ = 1 surfaces were computed without taking into account Doppler shifts, at the centers of lines of Mg ii k, and several lines of Fe ii. The x–y images of height of formation are plotted in order of decreasing opacity from Mg ii to Fe ii 2769.75 Å. In the bottom right panel, slices of these τ = 1 surfaces are shown, taken along the black line in the five other panels. But the black lines in this final panel are magnetic lines of force in the y–z plane. Evidently, a combination of these and other lines of iron with a wide range of opacities spans the ranges of excursions of the surfaces away from a horizontal plane.

Link to paper: Measuring the Magnetic Origins of Solar Flares, Coronal Mass Ejections, and Space Weather

Responses of the Thermosphere and Ionosphere System to Concurrent Solar Flares and Geomagnetic Storms

kolinski — Wed, 17 Nov 2021 17:13:03 +0000

Responses of the Thermosphere and Ionosphere System to Concurrent Solar Flares and Geomagnetic Storms kolinski Wed, 11/17/2021 - 10:13

Publication Name: JGR; Author's Names: Liying Qian, Wenbin Wang, Alan G. Burns, Phillip C. Chamberlin, Stanley C. Solomon

Author:

kolinski

Nov 17, 2021

We conducted numerical simulations to examine dayside thermosphere and ionosphere responses to concurrent solar flares and a geomagnetic storm during September 6th – September 11th, 2017, as well as the interplay of flare and storm effects. We found that E-region electron density response to the flares was much smaller inside the auroral oval than it was outside the auroral oval due to an extra source of ionization by auroral particle precipitation. During quiet times in this period, flare enhanced ionization, which decreased daytime eastward electric fields, caused an initial weakening of the vertical E x B drifts.

The simulated vertical E x B drift velocity (Wi), and the changes of the vertical drift velocity due to the flares, at 300 km and12:00 LT (September 6th – September 11th, 2017). (a) Wi using the flare spectrum and observed Kp; (b) Wi using the daily spectrum and observed Kp; (c) the difference between (a) and (b), which is the response to the flares in the presence of the storm; (d) the GOES X-ray energy flux in 0.1 – 0.8nm; (e) the Dst index. The vertical dashed lines indicate the flare peaks.

This weakening of the vertical E x B drifts was on the order of ~ 20% for an X8.2 flare in this period. During storm times, flare-induced initial changes of the vertical plasma drifts varied between being positive and being negative, depending on latitudes, due to storm-time disturbance dynamo effects. Storm effects also overall weakened flare effects on geopotential height, ionospheric F2 peak height hmF2, and ionospheric F2 peak electron density NmF2. In addition, storm effects changed the latitudinal distributions of flare effects on hmF2, NmF2, vertical plasma drifts, and O/N2. On the other hand, no major X-class flare occurred shortly before or during the storm. Model simulations indicate that the weaker C- and M- class flares that occurred before and during the storm had a minor effect on the amplitude of the large-scale traveling atmosphere disturbances generated by the storm.

Measuring the magnetic origins of solar flares, CMEs and Space Weather

kolinski — Mon, 15 Nov 2021 22:54:57 +0000

Measuring the magnetic origins of solar flares, CMEs and Space Weather kolinski Mon, 11/15/2021 - 15:54

Publication: ApJ; First HAO Author: Philip Judge

Author:

kolinski

Nov 15, 2021

We take a broad look at the problem of identifying the magnetic solar causes of space weather. The challenges are best met through a combination of near UV lines of bright Mg II, and lines of Fe II and Fe I (mostly within the 4s − 4p transition array) which form in the chromosphere up to 20,000 K. Both Hanle and Zeeman effects can in principle be used to derive vector magnetic fields. However, for any given spectral line the τ = 1 surfaces are generally geometrically corrugated owing to fine structure such as fibrils and spicules.

A smoothed UV spectrum of α alpha Cen A, obtained by the Hubble Space Telescope, is displayed as a proxy for the mean solar intensity spectrum. The large number of lines of Fe I and Fe II are indicated and annotated with their mul- tiplet terms. The Mg II spectrum is also annotated including the 3s − 3p h and k lines, and the 3p − 3d lines.

By using multiple spectral lines spanning different optical depths, magnetic fields across nearly-horizontal surfaces can be inferred in regions of low plasma β, from which free energies, magnetic topology and other quantities can be derived.

Geospace response to an extreme solar flare

kolinski — Mon, 15 Nov 2021 21:58:00 +0000

Geospace response to an extreme solar flare kolinski Mon, 11/15/2021 - 14:58

Publication Name: AGU Advances; HAO Author: Jing Liu; Authors names as listed: Jing Liu, Wenbin Wang, Liying Qian, William Lotko, Alan G. Burns, Kevin Pham, Gang Lu, Stanley C. Solomon, et al.

Author:

kolinski

Nov 15, 2021

Solar flares—a sudden eruption of electromagnetic radiation at the Sun—are known to have significant impacts on Earth’s upper atmosphere and ionosphere, but their collective effects on geospace as an integrated system have never been examined. We use a newly developed whole geospace model, combined with key observational data, to study the effects of the 6 September 2017 X9.3 flare on the geospace system.

Solar flare effects on magnetospheric convection and ionospheric potential. Comparison of 50-minute averages (12:02-12:51 UT) from LTR simulations of magnetospheric and ionospheric states on September 6, 2017 with and without solar flare effects. Bottom row: LTR-simulated magnetospheric convection velocity in equatorial plane (ZGSM = 0) with (A) and without (B) solar flare effects and their difference (C). Arrows indicate direction and magnitude (also in color) of the convection velocity projected onto the plane. Top row: High-latitude electric potential, essentially convection streamlines in the ionosphere with (D) and without (E) solar flare effects and their difference (F). The minimum and maximum potentials are labeled below panels (D-F).

The analysis shows that the solar wind-magnetosphere interaction, magnetotail, field-aligned current distribution, auroral precipitation and high-latitude ionospheric convection respond to atmospheric absorption of solar flare radiation. This study, for the first time, demonstrates that a rapid and large increase in the iono-spheric E-region photoionization due to a solar transient event globally modifies the electrodynamic cou-pling of the geospace system.

solar flare

AAS Nova Features a Recent Publication by Philip Judge

Recent News

Responses of the Thermosphere and Ionosphere System to Concurrent Solar Flares and Geomagnetic Storms

Recent News

Measuring the magnetic origins of solar flares, CMEs and Space Weather

Recent News

Geospace response to an extreme solar flare

Recent News