Direct correlations between coronal transients and interplanetary disturbances

Abstract

Major interplanetary shock waves have often been successfully associated with major solar flares. The interplanetary response to weaker solar events, e.g., eruptive prominences (EP) and slow coronal transients, is far less pronounced. Recently, progress has been made by combining the newly-available data of white-light-coronagraph measurements from the earth-orbiting satellite P78/1 (these data show the development of coronal transients between 2.5 and 10 R _bd, in-situ plasma measurements from the HELIOS solar probes positioned mostly above the Sun's limb at solar distances between 60 and 200 R _bd (showing the reactions of the interplanetary plasma), ground based Hα-coronagraphs (showing in a few cases the evolution of EP's from the Sun's limb up to 1.5 A_bd).

In the years 1979 to 1981 about 25 uniquely associated events were identified, 19 of which allow some detailed analysis. The events can be sorted into three main categories:

• The ‘flare-type’: 13 events, probably all of them flare-related, transient speeds v _t from 560 to 1460 km s⁻¹, no evidence for post-acceleration of the transient (indicating impulsive injection), all transients followed by drastic interplanetary shock waves, some of them probably involving magnetic clouds.

• The ‘EP-type’: 4 events, none of them flare-related, at least one was observed as an Hα-EP, transient speed from 200 to 410 km s^-1, all post-accelerated (indicating ‘driven’ injection), all followed by shocks with at least one magnetic cloud, one showing presence of He⁺ and O²⁺ behind the shock.

• The ‘NCDE-type’: 2 events, one observed as an Hα-EP, the other without known solar source, v _t , = 130 and 470 km s⁻¹, one post-accelerated, the other one not, considerable density increase in interplanetary plasma (however, in pressure equilibrium with surroundings), one event including shock, the other not. These two events may not belong to the same category.

Our results are not completely consistent with previous work which is mainly based on data from the Skylab era, 1973/74. This could be due to the different phase in the solar cycle. The study is being continued.