With RHESSI data from five solar flares taken from beginning to end,we investigate the power conversion factorμdefined as the ratio of the time derivative of total thermal energy(ERHESSI+Erad+Econd)and the kinetic power(PRHESSI)of nonthermal electrons.Here, ERHESSI is the computed energy contained in thermal plasmas traced by RHESSI SXRs.Other two contributions(Erad and Econd)to the total energy are the energies lost through radiation and conduction,both of which can be derived from the observational data.If both are not considered,μis only positive before the SXR maximum.However,we find that for each flare studiedμis positive over the whole duration of the soalr flare after taking into account both radiation and conduction.Mean values forμrange from 11.7% to 34.6%for these five events,indicating roughly that about this fraction of the known energy in nonthermal electrons is efficiently transformed into thermal energy from start to end.This fraction is traced by RHESSI SXR observations;the rest is lost.The bulk of the nonthermal energy could heat the plasma low in the atmosphere to drive mass flows(i.e.chromospheric evaporation).
We have examined the Wind data in 1996 and identified 21 small interplanetary magnetic flux ropes(SIMFRs),and all the 21 SIMFRs have boundary layer structures.The durations of the boundary layers varied from several minutes to 30 minutes.These boundary layers also have properties of high proton temperature,density,and plasma beta.These boundary layers are formed by magnetic reconnections.In addition,in three events magnetic reconnections were occurring inside the boundary layers.It indicates that the flux rope structures have propagated for some period of time,and their boundaries were still evolving through interaction with the background solar wind.Namely it is very possible that the SIMFRs came from the solar corona.
