A case study of medium-scale travelling ionospheric disturbances (TIDs) that are correlated with solar wind Alfvén waves is presented. The HF radar groundscatter signatures of TIDs caused by atmospheric gravity waves with periods of 20–40 min are traced to a source at high latitudes, namely pulsed ionospheric flows (PIFs) due to bursts in the convection electric field and/or the associated iono...

From June 1994 to December 1995 the Ulysses spacecraft was within 3 AU of the Sun and traveled from high southern to high northern heliospheric latitudes. For this period, SWOOPS instrument data obtained when the magnetic field was approximately aligned with the radial direction from the Sun have been analyzed. In the fast wind at high latitudes, two resolvable proton components are typically p...

MHD-scale fluctuations in the velocity, magnetic, and density fields of the solar wind are routinely observed. The evolution of these fluctuations, as they are transported radially outwards by the solar wind, is believed to involve both wave and turbulence processes. The presence of an average magnetic field has important implications for the anisotropy of the fluctuations and the nature of the...

A theory of incompressible MHD turbulence recently developed by Boldyrev predicts the existence of a scale dependent angle of alignment between velocity and magnetic field fluctuations that is proportional to the lengthscale of the fluctuations to the power 1/4. In this study, plasma and magnetic field data from the Wind spacecraft are used to investigate the angle between velocity and magnetic...

Ulysses plasma data at high heliographic latitudes were studied to develop constraints on the structure of the corona at the base of the high-speed solar wind. Salient features of the flow poleward of ±60◦ revealed: 1) low variances of all bulk flow parameters, 2) parameter values that agree with those measured during high-speed conditions in the ecliptic plane when all are scaled to 1AU, 3) th...

We present a four-category classification algorithm for the solar wind, based on Gaussian Process. The four categories are the ones previously adopted in Xu and Borovsky (2015): ejecta, coronal hole origin plasma, streamer belt origin plasma, and sector reversal origin plasma. The algorithm is trained and tested on a labeled portion of the OMNI data set. It uses seven inputs: the solar wind spe...

The Very Local Interstellar Medium (VLISM) contains clouds which consist of partially-ionized plasma. These clouds can be effectively diagnosed via high resolution optical and ultraviolet spectroscopy of the absorption lines they form in the spectra of nearby stars. Information provided by these spectroscopic measurements includes values for ξ , the root-mean-square velocity fluctuation due to ...

Abstract. It is known that the ionospheric cross polar cap potential (CPCP) saturates when the interplanetary magnetic field (IMF) Bz becomes very large. Few studies have offered physical explanations as to why the polar cap potential saturates. We present 13 events in which the reconnection electric field (REF) goes above 12 mV/m at some time. When these events are examined as typically done i...

We report the simultaneous observation of 1.6– 1.7 mHz pulsations in the ionospheric F-region with the CUTLASS bistatic HF radar and an HF Doppler sounder, on the ground with the IMAGE and SAMNET magnetometer arrays, and in the upstream solar wind. CUTLASS was at the time being operated in a special mode optimized for high resolution studies of ULF waves. A novel use is made of the ground retur...

We show that local directional alignment of the velocity and magnetic field fluctuations occurs rapidly in magnetohydrodynamics for a variety of parameters and is seen both in direct numerical simulations and in solar wind data. The phenomenon is due to an alignment between magnetic field and gradients of either pressure or kinetic energy, and is similar to alignment of velocity and vorticity i...