Global Energetics of Solar Flares: III. Non thermal Energies

This study entails the third part of a global flare energetics project, in which Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) data of 191 M and X-class flare events from the first 3.5 yrs of the Solar Dynamics Observatory (SDO) mission are analyzed. We fit a thermal and a nonthermal component to RHESSI spectra, yielding the temperature of the differential emission measure (DEM) tail, the nonthermal power law slope and flux, and the thermal/nonthermal cross-over energy $e_{\mathrm{co}}$. From these parameters we calculate the total nonthermal energy $E_{\mathrm{nt}}$ in electrons with two different methods: (i) using the observed cross-over energy $e_{\mathrm{co}}$ as low-energy cutoff, and (ii) using the low-energy cutoff $e_{\mathrm{wt}}$ predicted by the warm thick-target bremsstrahlung model of Kontar et al. {\bf Based on a mean temperature of $T_e=8.6$ MK in active regions we find low-energy cutoff energies of $e_{\mathrm{wt}} =6.2\pm 1.6$ keV for the warm-target model, which is significantly lower than the cross-over energies $e_{\mathrm{co}}=21 \pm 6$ keV. Comparing with the statistics of magnetically dissipated energies $E_{\mathrm{mag}}$ and thermal energies $E_{\mathrm{th}}$ from the two previous studies, we find the following mean (logarithmic) energy ratios with the warm-target model: $E_{\mathrm{nt}} = 0.41 \ E_{\mathrm{mag}}$, $E_{\mathrm{th}} = 0.08 \ E_{\mathrm{mag}}$, and $E_{\mathrm{th}} = 0.15 \ E_{\mathrm{nt}}$. The total dissipated magnetic energy exceeds the thermal energy in 95% and the nonthermal energy in 71% of the flare events, which confirms that magnetic reconnection processes are sufficient to explain flare energies. The nonthermal energy exceeds the thermal energy in 85\% of the events, which largely confirms the warm thick-target model.Comment: 34p, 9 Figs., 1 Tabl

Three-dimensional magnetic reconnection in a collapsing coronal loop system

Context. Magnetic reconnection is believed to be the primary mechanism by which non-potential energy stored in coronal magnetic fields is rapidly released during solar eruptive events. Unfortunately, owing to the small spatial scales on which reconnection is thought to occur, it is not directly observable in the solar corona. However, larger scale processes, such as associated inflow and outflow, and signatures of accelerated particles have been put forward as evidence of reconnection. Aims. Using a combination of observations we explore the origin of a persistent Type I radio source that accompanies a coronal X-shaped structure during its passage across the disk. Of particular interest is the time range around a partial collapse of the structure that is associated with inflow, outflow, and signatures of particle acceleration. Methods. Imaging radio observations from the Nançay Radioheliograph were used to localise the radio source. Solar Dynamics Observatory (SDO) AIA extreme ultraviolet (EUV) observations from the same time period were analysed, looking for evidence of inflows and outflows. Further mpol

HELIO Use Case 3: HELIO as a Tool for Space Weather

<p>The Challenge: <br>To use HELIO to study a number of periods of elevated space weatherat Earth and to identify the system’s strengths and weaknesses.</p

What is the Astrophysics Research Group at TCD doing to understand Space Weather?

<div> What is the Astrophysics Research Group at TCD doing to understand Space Weather? <div> <p>Poster presented during <a href="http://www.irishmetsociety.org/ims-conference-2012" rel="nofollow">"The Science of Weather Forecasting"</a> conference organized by the <a href="http://www.irishmetsociety.org" rel="nofollow">Irish Metereological Society</a> in Dublin on March 24, 2012.</p> <p>Extra material, bibliography and links:<br><a href="http://www.tcd.ie/Physics/Astrophysics/" rel="nofollow">Astrophysics Research Group</a> at <a href="http://www.tcd.ie" rel="nofollow">Trinity College Dublin</a><br><a href="http://www.solarmonitor.org" rel="nofollow">www.solarmonitor.org</a><br><a href="http://www.rosseobservatory.ie" rel="nofollow">Rosse Observatory</a> at <a href="http://www.birrcastle.com" rel="nofollow">Birr Castle</a>, Co. Offaly, Ireland.<br>Space weather effects image comes from a modified version of <a href="http://www.spaceweather.eu/en/node/187" rel="nofollow">Jan Wera's image</a>.<br>Events on the time line comes from <a href="http://dx.doi.org/10.1007/978-3-540-34578-7_9" rel="nofollow">Space weather effects on Communication</a> by Lanzerotti (2007) [<a href="http://solar.njit.edu/preprints/lanzerotti1284.pdf" rel="nofollow">e-print</a>].<br>SMART code is described in <a href="http://dx.doi.org/10.1016/j.asr.2010.06.024" rel="nofollow">Solar Magnetic Feature Detection and Tracking for Space Weather Monitoring"</a> (Higgins et al., 2010) [<a href="http://arxiv.org/abs/1006.5898v1" rel="nofollow">e-print</a>].<br>Magnetic extrapolation comes from a modified version of Figure 10 in <a href="http://dx.doi.org/10.1051/0004-6361/201014416" rel="nofollow">"Testing magnetofrictional extrapolation with the Titov-Démoulin model of solar active regions"</a> by Valori et al. (2010) [<a href="http://arxiv.org/abs/1005.0254" rel="nofollow">e-print</a>].<br>Solar images from SOHO/EIT, SoHO/MDI, SDO/AIA and SDO/HMI instruments obtained using <a href="http://helioviewer.org/" rel="nofollow">Helioviewer.org</a>.<br>Radio shock observed on April 20, 1998 from <a href="http://www.obs-nancay.fr/" rel="nofollow">Nançay Radioheliograph</a> (France).<br>Flare model cartoon is a modifed version of <a href="http://www.cora.nwra.com/%7Ewerne/eos/text/flare.html" rel="nofollow"> flare diagram</a>.<br>Space weather session at <a href="http://esof2012.org/" rel="nofollow">Euroscience Open Forum 2012</a> will happen at 13'30 on July 15, 2012.</p> </div> </div

A Comprehensive Overview of the 2011 June 7 Solar Storm

<p>Poster presented at the "Solar in Sonoma: Tracing the Connections in Solar Eruptive Events" conference, November 27th - December 2nd 2012, Petaluma, CA, USA.</p