About Steady and Transient States During Two Long Intervals of Extremely Low Speed Solar Wind Speed Observed by STEREO and Wind
Abstract
The passage of a solar wind stream extending from October 24 to 30, 2010, was well monitored, ahead of arrival at Earth's location of a possible corotating stream, with the help of the STEREO-A instruments IMPACT and PLASTIC. This was an extremely slow flow which exhibited the following features
a. An interval of over 2 days of speeds below 250 km/s b. At the start, an expanding magnetic cloud interval lasting about 14 hrs. c. The presence of distinct ratios in charge states suggesting presence of transient material in and outside the magnetic cloud. d. The presence in the plasma of a sizeable amount of He++ which we compare with the predictions made at the observed SW speed. We check with Lopez (1987) the observed and predicted estimates of the thermal velocity of the protons observed for the interval. In addition, we present the implication on the Parker model for the possible temperature of the corona assuming the dominant aspects of the outflow correspond to the case of an steady solar wind. The lack of passage of the event near Earth location is discussed, and its implications regarding the spatial extent of the solar outflow and the nature of its overall origin is assessed. Although not on year 2010, at the Lagrangian point L1, we observe with Wind the occurrence in years 2007 to 2009 of several intervals of low speed solar wind, of which for a comparison we select the low solar wind interval starting Dec 8, 2009 and which continued for more than 5 days. The interval at Wind has a similar extension as the one at STEREO-A. This includes the presence of a MC. Charge states are compared as well as the presence of the alpha-to-proton number density ratio- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2016)
- Pub Date:
- July 2016
- Bibcode:
- 2016shin.confE..76B