Evidence for the prolonged existence of >100 MeV solar protons in coronal structures

Solar proton events (SPEs) of 1989–1992 accompanied by ground-level enhancements of the cosmic-ray intensity are analyzed. A diffusive-propagation model can well approximate the solar proton intensity at energies of 84–200 MeV measured on board the GOES-7 satellite during the first 15–20 hours of the development of an SPE, assuming several episodes of proton injection into interplanetary space over some hours. The detection of π⁰-decay gamma-ray emission during the flares of June 11 and 15, 1991 on board the CGRO and GAMMA-1 space observatories is the sole experimental evidence for the existence of protons with energies >100 MeV near the Sun over such extended times. The number of protons in the source is estimated for various times based on the propagation model. Moreover, this value is in qualitative and quantitative agreement with the number of protons required to generate the observed gamma-ray emission for the June 15, 1991 event (and in qualitative agreement for the June 11, 1991 event). This provides evidence that processes of prolonged trapping and/or acceleration of protons in coronal structures may be possible in other such events.     

The Role of Long-Duration X-ray Solar Flares in the Generation of Interplanetary Disturbances

At present, it is widely believed that coronal mass ejections (CMEs) rather than solar flares, as assumed previously, are the sources of sporadic interplanetary disturbances. CMEs are an integral part of the powerful nonstationary processes that in many cases give rise to long-decay flares (LDFs). We numerically simulate the energy balance in a giant loop that forms during a LDF. For geoefficient disk flares, we show that maintaining the observed X-ray flux requires a prolonged input of a substantial amount of energy into this loop from above, from the region of primary energy release (probably, from a vertical current sheet). Part of the energy from this region propagates outward both at the onset of the process, with plasmoid ejections, and during the prolonged dynamic phase, thereby enhancing the CME. Using the series of LDFs in March 1993 as an example, we consider the role of flares in producing the corresponding interplanetary disturbances. The large amplitude of the Forbush effect and the strong interplanetary disturbance on March 8–10 near the Earth and on March 15 at a heliocentric distance of about 5 AU (Ulysses) are shown to have been associated with the long-duration flare of March 6, 1993. The March 1993 events give a typical example of CME and magnetic-configuration opening that result in post-CME energy release. This is accompanied by the appearance of new arch systems inside the active region and/or by the development of giant loop systems outside. Such a process enhances CME and increases its geoefficiency.     

Prolonged,Weak C1.2 Flares: A Source of Protons and Electrons

Geomagnetism and Aeronomy - Two proton events (>100 MeV; GOES, ACS SPI) associated with weak flares (C1.2, GOES class) in the soft X-ray range that occurred on November 26, 2011, and...