Search Publications
Relative outflow enhancements during major geomagnetic storms - Cluster observations
Nilsson, Hans; Slapak, Rikard; Schillings, Audrey +2 more
The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between…
High-Resolution Vector Magnetograms of the Sun's Poles from Hinode: Flux Distributions and Global Coronal Modeling
Petrie, Gordon
The Sun's polar fields play a leading role in structuring the large-scale solar atmosphere and in determining the interplanetary magnetic field. They are also believed to supply the seed field for the subsequent solar activity cycle. However, present-day synoptic observations do not have sufficient spatial resolution or sensitivity to diagnose acc…
Properties of the Closest Young Binaries. I. DF Tau’s Unequal Circumstellar Disk Evolution
Prato, L.; Schaefer, G.; Simon, M. +6 more
We present high-resolution, spatially resolved, near-infrared spectroscopy and imaging of the two components of DF Tau, a young, low-mass, visual binary in the Taurus star-forming region. With these data, we provide a more precise orbital solution for the system, determine component spectral types, radial velocity, veiling and v\sin i values, and …
Unusual void galaxy DDO 68: implications of the HST-resolved photometry
Makarova, L. N.; Makarov, D. I.; Pustilnik, S. A. +1 more
DDO 68 (UGC 5340) is an unusual dwarf galaxy with extremely low gas metallicity [12 + log (O/H) = 7.14] residing in the nearby Lynx-Cancer void. Despite its apparent isolation, it shows both optical and H I morphological evidence for strong tidal disturbance. Here, we study the resolved stellar populations of DDO 68 using deep images from the HST …
Sudden Penumbral Reappearance and Umbral Motion Induced by an M7.9 Solar Flare
Yang, Jiayan; Hong, Junchao; Xu, Zhe +2 more
The sudden flare-related changes of sunspot structures have been recognized as the photospheric responses to the solar eruptions in the corona. In this study, we report two distinctive sunspots variations associated with the flare SOL2015-06-25T08:16 (M7.9). Along the flaring polarity inversion line (PIL), the originally decayed penumbra showed a …
Statistical study of the alteration of the magnetic structure of magnetic clouds in the Earth's magnetosheath
Escoubet, C. P.; Kilpua, E. K. J.; Turc, L. +2 more
The magnetosheath plays a central role in the solar wind-magnetospheric coupling. Yet the effects of its crossing on solar wind structures such as magnetic clouds (MCs) are generally overlooked when assessing their geoeffectivity. Using 82 MCs observed simultaneously in the solar wind and the magnetosheath, we carry out the first statistical study…
Comparative study of three reconnection X line models at the Earth's dayside magnetopause using in situ observations
Walsh, B. M.; Sibeck, D. G.; Gonzalez, W. D. +3 more
This work examines the large-scale aspects of magnetic field reconnection at the Earth's dayside magnetopause. We use two sets of reconnection events, which are identified mostly by the in situ detection of accelerated and Alfvénic plasma flows. We intercompare three analytical models that predict the reconnection X line location and orientation, …
Observations of Reconnection Flows in a Flare on the Solar Disk
Fletcher, L.; Hannah, I. G.; Jeffrey, N. L. S. +3 more
Magnetic reconnection is a well-accepted part of the theory of solar eruptive events, though the evidence is still circumstantial. Intrinsic to the reconnection picture of a solar eruptive event, particularly in the standard model for two-ribbon flares (CSHKP model), are an advective flow of magnetized plasma into the reconnection region, expansio…
Multi-instrument observation of simultaneous polar cap auroras on open and closed magnetic field lines
Lester, M.; Fear, R. C.; Zhang, Y. +5 more
This paper presents observations of polar cap auroral features on 19 January 2008, evaluated using multiple instruments with near-simultaneous observations in both hemispheres. Analysis of the features indicates that there are at least two formation mechanisms/types of polar cap aurora occurring simultaneously on different magnetic field topologie…
Radio observations of globulettes in the Carina nebula
Persson, C. M.; Gahm, G. F.; Grenman, T. +2 more
Context. The Carina nebula hosts a large number of globulettes. An optical study of these tiny molecular clouds shows that the majority are of planetary mass, but there are also those with masses of several tens up to a few hundred Jupiter masses.
Aims: We seek to search for, and hopefully detect, molecular line emission from some of the more…