Breakthrough Listen

Abstract:

Interplanetary scintillation (IPS) observations provide views of the solar wind at all heliographic latitudes from near 1 A.U. down to fields of view covered by coronagraphs. These observations can be used to study the propagation of the solar wind and solar transients out into interplanetary space, and also measure the inner-heliospheric response to co-rotating solar structures and coronal mass ejections (CMEs). We use a three dimensional (3D) reconstruction technique that obtains perspective views from solar co-rotating plasma and outward-flowing solar wind as observed from the Earth by iteratively fitting a kinematic solar wind model to IPS data from various observing systems. Here we use the model with both Solar Terrestrial Environment Laboratory (STELab), Japan, and Ootacamund (Ooty) Radio Telescope (ORT), India, IPS observations. This 3D modeling technique permits reconstructions of the density and velocity structures of CMEs and other interplanetary transients at a relatively coarse resolution for STELab and better for Ooty; and is dependent upon the number of observations. We present 3D reconstructions of CME events around 4-8 November 2004 from Ooty IPS observations and some preliminary reconstructions of STELab IPS observations around the Whole Heliospheric Interval (WHI). We also present some preliminary results of a CME observation by both the European Incoherent SCATter (EISCAT) radar IPS observations and those made by the Solar TErrestrial RElations Observatory (STEREO) of a CME in May 2007.

Abstract:

We describe simultaneous Interplanetary Scintillation (IPS) and STEREO Heliospheric Imager (HI) observations of a coronal mass ejection (CME) on 16 May 2007. Strong CME signatures were present throughout the IPS observation. The IPS raypath lay within the field‐of‐view of HI‐1 on STEREO‐A and comparison of the observations shows that the IPS measurements came from a region within a faint CME front observed by HI‐1A. This front may represent the merging of two converging CMEs. Plane‐of‐sky velocity estimates based on time‐height plots of the two converging CME structures were 325 kms−1 and 550 kms−1 for the leading and trailing fronts respectively. The plane‐of‐sky velocities determined from IPS ranged from 420 ± 10 kms−1 to 520 ± 20 kms−1. IPS results reveal the presence of micro‐structure within the CME front which may represent interaction between the two separate CME events. This is the first time that it has been possible to interpret IPS observations of small‐scale structure within an interplanetary CME in terms of the global structure of the event.