Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe

Context. Periodicities have frequently been reported across many wavelengths in the solar corona. Correlated periods of ~5 minutes, comparable to solar p-modes, are suggestive of coupling between the photosphere and the corona. Aims. Our study investigates whether there are correlations in the periodic behavior of Type III radio bursts, indicative of non-thermal electron acceleration processes, and coronal EUV emission, assessing heating and cooling, in an active region when there are no large flares. Methods. We use coordinated observations of Type III radio bursts from the FIELDS instrument on Parker Solar Probe (PSP), of extreme ultraviolet emissions by the Solar Dynamics Observatory (SDO)/AIA and white light observations by SDO/HMI, and of solar flare x-rays by Nuclear Spectroscopic Telescope Array (NuSTAR) on April 12, 2019. Several methods for assessing periodicities are utilized and compared to validate periods obtained. Results. Periodicities of about 5 minutes in the EUV in several areas of an active region are well correlated with the repetition rate of the Type III radio bursts observed on both PSP and Wind. Detrended 211A and 171A light curves show periodic profiles in multiple locations, with 171A peaks lagging those seen in 211A. This is suggestive of impulsive events that result in heating and then cooling in the lower corona. NuSTAR x-rays provide evidence for at least one microflare during the interval of Type III bursts, but there is not a one-to-one correspondence between the x-rays and the Type-III bursts. Our study provides evidence for periodic acceleration of non-thermal electrons (required to generate Type III radio bursts) when there were no observable flares either in the x-ray data or the EUV. The acceleration process, therefore, must be associated with small impulsive events, perhaps nanoflares

Parp1 hyperactivity couples DNA breaks to aberrant neuronal calcium signalling and lethal seizures

Defects in DNA single-strand break repair (SSBR) are linked with neurological dysfunction but the underlying mechanisms remain poorly understood. Here, we show that hyperactivity of the DNA strand break sensor protein Parp1 in mice in which the central SSBR protein Xrcc1 is conditionally deleted (Xrcc1Nes-Cre) results in lethal seizures and shortened lifespan. Using electrophysiological recording and synaptic imaging approaches, we demonstrate that aberrant Parp1 activation triggers seizure-like activity in Xrcc1-defective hippocampus ex vivo and deregulated presynaptic calcium signalling in isolated hippocampal neurons in vitro. Moreover, we show that these defects are prevented by Parp1 inhibition or deletion and, in the case of Parp1 deletion, that the lifespan of Xrcc1Nes-Cre mice is greatly extended. This is the first demonstration that lethal seizures can be triggered by aberrant Parp1 activity at unrepaired SSBs, highlighting PARP inhibition as a possible therapeutic approach in hereditary neurological disease

Not a Second Time? John Lennon’s Aeolian Cadence Reconsidered

In 1963 William Mann coined the term “aeolian cadence” to describe a harmonic progression in the song “Not a Second Time” by the Beatles. This term has caused confusion ever since. In this article, I discuss why Mann might have used this confusing phrase and how it relates to this song by John Lennon. I will argue that, in the debate that ensued from Mann’s observations, his commentators were primarily preoccupied with terminology and definitions but forgot to listen to Lennon. More specifically, I argue that, if the interplay between the music and lyrics is considered, the famous cadence in “Not a Second Time” can best be interpreted as “deceptive.

Periodicities in an active region correlated with Type III radio bursts observed by Parker Solar Probe

ContextPeriodicities have frequently been reported across many wavelengths in the solar corona. Correlated periods of ~5 min, comparable to solar p-modes, are suggestive of coupling between the photosphere and the corona.AimsOur study investigates whether there are correlations in the periodic behavior of Type III radio bursts which are indicative of nonthermal electron acceleration processes, and coronal extreme ultraviolet (EUV) emission used to assess heating and cooling in an active region when there are no large flares.MethodsWe used coordinated observations of Type III radio bursts from the FIELDS instrument on Parker Solar Probe (PSP), of EUV emissions by the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) and white light observations by SDO Helioseismic and Magnetic Image (HMI), and of solar flare X-rays by Nuclear Spectroscopic Telescope Array (NuSTAR) on April 12, 2019. Several methods for assessing periodicities are utilized and compared to validate periods obtained.ResultsPeriodicities of ~5 min in the EUV in several areas of an active region are well correlated with the repetition rate of the Type III radio bursts observed on both PSP and Wind. Detrended 211 and 171 Å light curves show periodic profiles in multiple locations, with 171 Å peaks sometimes lagging those seen in 211 Å. This is suggestive of impulsive events that result in heating and then cooling in the lower corona. NuSTAR X-rays provide evidence for at least one microflare during the interval of Type III bursts, but there is not a one-to-one correspondence between the X-rays and the Type III bursts. Our study provides evidence for periodic acceleration of nonthermal electrons (required to generate Type III radio bursts) when there were no observable flares either in the X-ray data or the EUV. The acceleration process, therefore, must be associated with small impulsive events, perhaps nanoflares

Measurement of the open magnetic flux in the inner heliosphere down to 0.13 AU

International audienceContext. Robustly interpreting sets of in situ spacecraft data of the heliospheric magnetic field (HMF) for the purpose of probing the total unsigned magnetic flux in the heliosphere is critical for constraining global coronal models as well as understanding the large scale structure of the heliosphere itself. The heliospheric flux (ΦH) is expected to be a spatially conserved quantity with a possible secular dependence on the solar cycle and equal to the measured radial component of the HMF weighted by the square of the measurement's heliographic distance (BRR2). It is also expected to constitute a direct measurement of the total unsigned magnetic flux escaping the corona (Φopen). Previous work indicates that measurements of ΦH exceed the value predicted by standard coronal models (the "open flux problem"). However, the value of the open flux derived from in situ measurements remains uncertain because it depends on the method employed to derive it. Past derivations also pointed towards an increase in ΦH with heliocentric distance, although this may also be related to its method of computation. Aims: In this work, we attempt to determine a more robust estimate of the heliospheric magnetic flux (ΦH) using data from the FIELDS instrument on board Parker Solar Probe (PSP), to analyse how susceptible it is to overestimation and a dependence on time and space, as well as considering how it compares to simple estimates of Φopen from potential field source surface (PFSS) models. Methods: We compared computations of the heliospheric magnetic flux using different methods of data processing on magnetic field data from PSP, STEREO A, and Wind. Measured radial trends in fluctuations and background magnetic structure were used to generate synthetic data to analyse their effect on the estimate of BRR2. The resulting best estimates were computed as a function of time and space and then compared to estimates from PFSS models. Results: Radially varying fluctuations of the HMF vector as well as large-scale variations in the inclination of the Parker spiral angle are shown to have a non-trivial effect on the 1D distributions of BRR2. This causes the standard statistical metrics of the mean and mode (the most probable values) to evolve with radius, independently of the central value about which the vector fluctuates. In particular, the mean systematically underestimates ΦH for R −0.6+0.3 nT AU2. To the extent probed by PSP, no strong dependence on latitude or longitude is apparent, although at 1 AU, the spread of measured values appears to grow at the highest latitudes. The best estimate of the heliospheric flux is significantly larger than estimates from PFSS models studied here, which predict values from 1.2-1.8 nT AU2, depending on the choice of magnetogram or source surface height. Conclusions: Of the methods for computing the heliospheric flux over a wide range of heliocentric distances using only magnetic field data considered in this work, the most robust choice is to use the PSM. The decay of fluctuations and weakening importance of local flux inversions at smaller heliocentric distances indicate that the measurement is most accurate close to the sun and that it is justified for us to consider that ΦH ~ Φopen for these measurements. The determined value is too high to be explained via PFSS models. Contemporary magnetohydrodynamic models with the same photospheric input are unlikely to close this gap. Therefore, the most likely solutions remain in improvements of coronal models, for example, through improved boundary conditions via the direct measurement of the photospheric field in the solar polar regions or through the inclusion of missing physical processes such as time-dependent or non-potential effects, which can produce a contribution to the open flux that is not rooted in obvious coronal holes

Gastric bypass increases energy expenditure in rats

BACKGROUND: Mechanisms underlying weight loss maintenance after gastric bypass surgery are poorly understood. Our aim was to examine the effects of gastric bypass on energy expenditure in rats. METHODS: Thirty diet-induced obese male Wistar rats underwent either gastric bypass (n=14), sham operation ad libitum fed (n=8) or sham-operation body weight-matched (n=8). Energy expenditure was measured in an open circuit calorimetry system. RESULTS: Body weight after 70 days was lower after gastric bypass compared to sham ad libitum fed rats (p<0.0001). Sham-operated body weight-matched controls ate less than gastric bypass animals to reach the same weight (16.2+/-0.5g vs. 27.5+/-0.8g, p<0.001). Twenty-four hour energy expenditure was increased after gastric bypass (4.50+/-0.04 kcal/kg/h) compared to sham-operated ad libitum fed (4.29+/-0.08 kcal/kg/h) and sham-operated body weight-matched controls (3.98+/-0.10 kcal/kg/h, p<0.001). Gastric bypass rats showed higher energy expenditure during the light phase than both sham-operated control groups (sham ad lib: 3.63+/-0.04 kcal/kg/h vs. sham body weight-matched: 3.42+/-0.05 kcal/kg/h vs. bypass: 4.12+/-0.03 kcal/kg/h, p<0.001). Diet-induced thermogenesis was elevated after gastric bypass compared to sham-operated body weight-matched controls three hours after a test meal (0.41+/-1.9% vs. 10.5+/-2.0%, p<0.05). The small bowel of gastric bypass rats was 72.1% heavier due to hypertrophy compared with sham-operated ad libitum fed rats (p<0.0001). CONCLUSIONS: Gastric bypass surgery in rats prevented the expected decrease in energy expenditure subsequent to weight loss. Diet-induced thermogenesis was higher after gastric bypass compared to body weight-matched controls. Raised energy expenditure may be an additional mechanism explaining the physiological basis of weight loss after gastric bypass surgery