Type 2 solar radio events observed in the interplanetary medium. Part 1: General characteristics

Twelve type 2 solar radio events were observed in the 2 MHz to 30 kHz frequency range by the radio astronomy experiment on the ISEE-3 satellite over the period from September 1978 to December 1979. These data provide the most comprehensive sample of type 2 radio bursts observed at kilometer wavelengths. Dynamic spectra of a number of events are presented. Where possible, the 12 events were associated with an initiating flare, ground based radio data, the passage of a shock at the spacecraft, and the sudden commencement of a geomagnetic storm. The general characteristics of kilometric type 2 bursts are discussed

Task constraints distinguish perspective inferences from perspective use during discourse interpretation in a false belief task

Interpreting other peoples’ actions relies on an understanding of their current mental states (e.g. beliefs, desires and intentions). In this paper, we distinguish between listeners’ ability to infer others’ perspectives and their explicit use of this knowledge to predict subsequent actions. In a visual-world study, two groups of participants (passive observers vs. active participants) watched short videos, depicting transfer events, where one character (‘Jane’) either held a true or false belief about an object’s location. We tracked participants’ eye-movements around the final visual scene, time-locked to related auditory descriptions (e.g. “Jane will look for the chocolates in the container on the left”.). Results showed that active participants had already inferred the character’s belief in the 1 s preview period prior to auditory onset, before it was possible to use this information to predict an outcome. Moreover, they used this inference to correctly anticipate reference to the object’s initial location on false belief trials at the earliest possible point (i.e. from “Jane” onwards). In contrast, passive observers only showed evidence of a belief inference from the onset of “Jane”, and did not show reliable use of this inference to predict Jane’s behaviour on false belief trials until much later, when the location (“left/right”) was auditorily available. These results show that active engagement in a task activates earlier inferences about others’ perspectives, and drives immediate use of this information to anticipate others’ actions, compared to passive observers, who are susceptible to influences from egocentric or reality biases. Finally, we review evidence that using other peoples’ perspectives to predict their behaviour is more cognitively effortful than simply using one’s own

Relativistic Proton Production During the 14 July 2000 Solar Event: The Case for Multiple Source Mechanisms

Protons accelerated to relativistic energies by transient solar and interplanetary phenomena caused a ground-level cosmic ray enhancement on 14 July 2000, Bastille Day. Near-Earth spacecraft measured the proton flux directly and ground-based observatories measured the secondary responses to higher energy protons. We have modelled the arrival of these relativistic protons at Earth using a technique which deduces the spectrum, arrival direction and anisotropy of the high-energy protons that produce increased responses in neutron monitors. To investigate the acceleration processes involved we have employed theoretical shock and stochastic acceleration spectral forms in our fits to spacecraft and neutron monitor data. During the rising phase of the event (10:45 UT and 10:50 UT) we find that the spectrum between 140 MeV and 4 GeV is best fitted by a shock acceleration spectrum. In contrast, the spectrum at the peak (10:55 UT and 11:00 UT) and in the declining phase (11:40 UT) is best fitted with a stochastic acceleration spectrum. We propose that at least two acceleration processes were responsible for the production of relativistic protons during the Bastille Day solar event: (1) protons were accelerated to relativistic energies by a shock, presumably a coronal mass ejection (CME). (2) protons were also accelerated to relativistic energies by stochastic processes initiated by magnetohydrodynamic (MHD) turbulence.Comment: 38 pages, 9 figures, accepted for publication in the Astrophysical Journal, January, 200

Spatial Relationship of Signatures of Interplanetary Coronal Mass Ejections

Interplanetary coronal mass ejections (ICMEs) are characterized by a number of signatures. In particular, we examine the relationship between Fe charge states and other signatures during ICMEs in solar cycle 23. Though enhanced Fe charge states characterize many ICMEs, average charge states vary from event to event, are more likely to be enhanced in faster or flare‐related ICMEs, and do not appear to depend on whether the ICME is a magnetic cloud. © 2003 American Institute of PhysicsPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87650/2/681_1.pd

On the Brightness and Waiting-time Distributions of a Type III Radio Storm observed by STEREO/WAVES

Type III solar radio storms, observed at frequencies below approximately 16 MHz by space borne radio experiments, correspond to the quasi-continuous, bursty emission of electron beams onto open field lines above active regions. The mechanisms by which a storm can persist in some cases for more than a solar rotation whilst exhibiting considerable radio activity are poorly understood. To address this issue, the statistical properties of a type III storm observed by the STEREO/WAVES radio experiment are presented, examining both the brightness distribution and (for the first time) the waiting-time distribution. Single power law behavior is observed in the number distribution as a function of brightness; the power law index is approximately 2.1 and is largely independent of frequency. The waiting-time distribution is found to be consistent with a piecewise-constant Poisson process. This indicates that during the storm individual type III bursts occur independently and suggests that the storm dynamics are consistent with avalanche type behavior in the underlying active region.Comment: 14 pages, 4 figures, 1 table. Accepted for publication in Astrophysical Journal Letter

Flare magnetic reconnection and relativistic particles in the 2003 October 28 event

An X17.2 solar flare occurred on 2003 October 28, accompanied by multi-wavelength emissions and a high flux of relativistic particles observed at 1AU. We present the analytic results of the TRACE, SOHO, RHESSI, ACE, GOES, hard X-ray (INTEGRAL satellite), radio (Onderejov radio telescope), and neutron monitor data. It is found that the inferred magnetic reconnection electric field correlates well with the hard X-ray, gamma-ray, and neutron emission at the Sun. Thus the flare's magnetic reconnection probably makes a crucial contribution to the prompt relativistic particles, which could be detected at 1 AU. Since the neutrons were emitted a few minutes before the injection of protons and electrons, we propose a magnetic-field evolution configuration to explain this delay. We do not exclude the effect of CME-driven shock, which probably plays an important role in the delayed gradual phase of solar energetic particles.Comment: 5 pages, 7 figures, accepted by A&

Strength of Coronal Mass Ejection-Driven Shocks Near the Sun, and Its Importance in Predicting Solar Energetic Particle Events

Coronal shocks are important structures, but there are no direct observations of them in solar and space physics. The strength of shocks plays a key role in shock-related phenomena, such as radio bursts and solar energetic particle (SEP) generation. This paper presents an improved method of calculating Alfven speed and shock strength near the Sun. This method is based on using as many observations as possible, rather than one-dimensional global models. Two events, a relatively slow CME on 2001 September 15 and a very fast CME on 2000 June 15, are selected to illustrate the calculation process. The calculation results suggest that the slow CME drove a strong shock, with Mach number of 3.43 - 4.18, while the fast CME drove a relatively weak shock, with Mach number of 1.90 - 3.21. This is consistent with the radio observations, which find a stronger and longer decameter-hectometric (DH) type II radio burst during the first event, and a short DH type II radio burst during the second event. In particular, the alculation results explain the observational fact that the slow CME produced a major solar energetic particle (SEP) event, while the fast CME did not. Through a comparison of the two events, the importance of shock strength in predicting SEP events is addressed

Width of Radio-Loud and Radio-Quiet CMEs

In the present paper we report on the difference in angular sizes between radio-loud and radio-quiet CMEs. For this purpose we compiled these two samples of events using Wind/WAVES and SOHO/LASCO observations obtained during 1996-2005. It is shown that the radio-loud CMEs are almost two times wider than the radio-quiet CMEs (considering expanding parts of CMEs). Furthermore we show that the radio-quiet CMEs have a narrow expanding bright part with a large extended diffusive structure. These results were obtained by measuring the CME widths in three different ways.Comment: Solar Physic, in pres