The Temperature Dependence of Solar Active Region Outflows

Spectroscopic observations with the EUV Imaging Spectrometer (EIS) on Hinode have revealed large areas of high speed outflows at the periphery of many solar active regions. These outflows are of interest because they may connect to the heliosphere and contribute to the solar wind. In this Letter we use slit rasters from EIS in combination with narrow band slot imaging to study the temperature dependence of an active region outflow and show that it is more complicated than previously thought. Outflows are observed primarily in emission lines from Fe XI - Fe XV. Observations at lower temperatures (Si VII), in contrast, show bright fan-like structures that are dominated by downflows. The morphology of the outflows is also different than that of the fans. This suggests that the fan loops, which often show apparent outflows in imaging data, are contained on closed field lines and are not directly related to the active region outflows.Comment: Movies are available online at: http://tcrb.nrl.navy.mil/~hwarren/temp/papers/flow_temperatures/ To be submitted to ApJ

Coronal and Interplanetary Environment of Large Solar Energetic Particle Events

Abstract We studied the properties of coronal mass ejections (CMEs) associated with large solar energetic particle (SEP) events during 1997-2002 and compared them with those of preceding CMEs from the same source region. The primary findings of this study are (1) High-intensity (> 50 protons cm −2 s −1 sr −1 ) events are more likely to be preceded by other wide CMEs

Parker Solar Probe Imaging of the Night Side of Venus

We present images of Venus from the Wide-Field Imager for Parker Solar Probe (WISPR) telescope on board the Parker Solar Probe (PSP) spacecraft, obtained during PSP's third and fourth flybys of Venus on 2020 July 11 and 2021 February 20, respectively. Thermal emission from the surface is observed on the night side, representing the shortest wavelength observations of this emission ever, the first detection of the Venusian surface by an optical telescope observing below 0.8 μm. Consistent with previous observations at 1 μm, the cooler highland areas are fainter than the surrounding lowlands. The irradiances measured by WISPR are consistent with model predictions assuming a surface temperature of T = 735 K. In addition to the thermal emission, the WISPR images also show bright nightglow emission at the limb, and we compare the WISPR intensities with previous spectroscopic measurements of the molecular oxygen nightglow lines from Venus Express

Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18

We report direct observations of the magnetic reconnection site during an eruptive process that occurred on 2003 November 18. The event started with a rapid expansion of a few magnetic arcades located over the east limb of the Sun and developed an energetic partial-halo coronal mass ejection (CME), a long current sheet, and a group of bright flare loops in the wake of the CME. It was observed by several instruments, both in space and on the ground, including the EUV Imaging Telescope, Ultraviolet Coronagraph Spectrometer, and Large Angle Spectrometric Coronagraph experiment on board the Solar and Heliospheric Observatory, the Reuven Ramaty High Energy Solar Spectroscopic Imager, and the Mauna Loa Solar Observatory Mark IV K-Coronameter. We combine the data from these instruments to investigate various properties of the eruptive process, including those around the current sheet. The maximum velocities of the CME leading edge and the core were 1939 and 1484 km s(-1), respectively. The average reconnection inflow velocities near the current sheet over different time intervals ranged from 10.5 to 106 km s(-1), and the average outflow velocities ranged from 460 to 1075 km s(-1). This leads to a corresponding rate of reconnection in terms of the Alfven Mach number MA ranging from 0.01 to 0.23. The composite of images from different instruments specifies explicitly how the different objects developed by a single eruptive process are related to one another