Relationship between Intensity of White-Light Flares and Proton Flux of Solar Energetic Particles
aa r X i v : . [ a s t r o - ph . S R ] J a n Relationship between Intensity of White-Light Flares and Proton Flux of SolarEnergetic Particles
Nengyi Huang , , Yan Xu , , and Haimin Wang ,
1. Space Weather Research Lab, Center for Solar-Terrestrial Research,New Jersey Institute of Technology323 Martin Luther King Blvd, Newark, NJ 07102-19822. Big Bear Solar Observatory,New Jersey Institute of Technology40386 North Shore Lane, Big Bear City, CA 92314Subject headings:
Sun: activity — Sun: flares — Sun: particle emissionSolar Energetic Particles (SEPs; see review by Reames 1999) are considered to be one of themost important kinds of events in terms of their effects on space weather. They are mostly in theform of as accelerated protons and heavy ions. The SEPs were found to be accelerated by magneticreconnection during solar flares (e.g. Mori et al. 1998; Bombardieri et al. 2008). They also can beaccelerated by shocks while CMEs are propagating in interplanetary space (e.g. Klein & Trottet2001; Roussev et al. 2004). Aschwanden (2012) found that both flare and CME shock plays im-portant roles. In the solar observations, white light flares (WLF) are considered as most energeticsignature of particles bombarding solar surface and associated with both hard X-ray (HXR) andGamma ray emissions (Hudson 2016). In our previous study, we found a close correlation betweenWLF intensities and the HXR power index (Huang et al. 2016). In this study, we focus on thecomparison between SEP flux and WLF intensities.According to the NOAA space environment services center, there were 43 SEP events recordedfrom 2010, when SDO was launched (Pesnell et al. 2012), to September 2017. The counts of SEPflux can be found at https://umbra.nascom.nasa.gov/SEP/ . In this study, WLFs are identi-fied using the 45 s WL data obtained by SDO/HMI (Pesnell et al. 2012; Schou et al. 2012). TheWL emission was visually detected in 15 flares above M5. The WL emission is characterized byequivalent area (EA, Wang et al. 2008; Huang et al. 2016), which is the integrated enhancement ofcontrast over the entire flare ribbons.By comparing the SEP and WLF lists, the events can be divided into three groups as shown inFigure 1. The 1st group includes SEP events that were not associated with WLFs. They are plottedusing solid circles (half) on y-axis indicating zero WL emission. Their X-ray flux (represented byGOES classes in different colors) does not correlate with the proton flux. As we can see, a C-classflare may have stronger proton flux than many X- and M-class flares. The 2nd group containsWLFs without SEP detected. Those events are represented by empty circles (half) on x-axis. Theevents in these two groups show that there is no correlation between WLFs and SEP in 39 out of 2 –47 events. This result indicates that the SEPs may not be accelerated in the region where flare-related magnetic reconnection takes place. In the 3rd group, we found eight SEP events, whichwere associated with WLFs, including 5 M-class (blue color) and 3 X-class (red color) flares. As wecan see in the plot, there is no clear correlation between SEP flux and EA of WLFs. For instance,the flare on Sep. 6, 2017 was the strongest WLF with EA almost an order of magnitude largerthan the second largest one. However, no obvious increase of proton flux was detected. The protonfluxes were already enhanced due to the SEP event on Sep. 5, 2017. There was no significantcontinued enhancement of proton flux associated this X9 flare on Sep. 6, 2017. On the other hand,another X-class flare on Mar. 7, 2012 has strong WL emission and is associated with the strongestSEP event.In summary, our preliminary results show that most ( > ]101001000 P r o t o n F l u x [ p f u ] Aug/04/2011Aug/09/2011Jan/23/2012 Mar/07/2012Mar/13/2012Jul/06/2012Jun/25/2015Sep/04/2017 Sep/06/2017 X9
Fig. 1.— Comparison of SEP events and WLFs. Solid circles represent SEP events and emptycircles represent WLFs, which were not associated with SEP events. Different colors indicate themagnitudes of flares: red for X-class, blue for M-class and green for C-class flares. 3 –
REFERENCES
Aschwanden, M. J. 2012, Space Sci. Rev., 171, 3Bombardieri, D. J., Duldig, M. L., Humble, J. E., & Michael, K. J. 2008, ApJ, 682, 1315Huang, N.-Y., Xu, Y., & Wang, H. 2016, Research in Astronomy and Astrophysics, 16, 177Hudson, H. S. 2016, Sol. Phys., 291, 1273Klein, K.-L., & Trottet, G. 2001, Space Sci. Rev., 95, 215Mori, K.-i., Sakai, J.-i., & Zhao, J. 1998, ApJ, 494, 430Pesnell, W. D., Thompson, B. J., & Chamberlin, P. C. 2012, Sol. Phys., 275, 3Reames, D. V. 1999, Space Sci. Rev., 90, 413Roussev, I. I., Sokolov, I. V., Forbes, T. G., et al. 2004, ApJ, 605, L73Schou, J., Scherrer, P. H., Bush, R. I., et al. 2012, Sol. Phys., 275, 229Wang, H., Jing, J., Tan, C., Wiegelmann, T., & Kubo, M. 2008, ApJ, 687, 658