Energization of the ring current by substorms

first_imgThe substorm process releases large amounts of energy into the magnetospheric system, although where the energy is transferred to and how it is partitioned remains an open question. In this study, we address whether the substorm process contributes a significant amount of energy to the ring current. The ring current is a highly variable region, and understanding the energization processes provides valuable insight into how substorm-ring current coupling may contribute to the generation of storm conditions and provide a source of energy for wave driving. In order to quantify the energy input into the ring current during the substorm process, we analyze Radiation Belt Storm Probes Ion Composition Experiment and Helium Oxygen Proton Electron ion flux measurements for H+, O+, and He+. The energy content of the ring current is estimated and binned spatially for L and magnetic local time. The results are combined with an independently derived substorm event list to perform a statistical analysis of variations in the ring current energy content with substorm phase. We show that the ring current energy is significantly higher in the expansion phase compared to the growth phase, with the energy enhancement persisting into the substorm recovery phase. The characteristics of the energy enhancement suggest the injection of energized ions from the tail plasma sheet following substorm onset. The local time variations indicate a loss of energetic H+ ions in the afternoon sector, likely due to wave-particle interactions. Overall, we find that the average energy input into the ring current is similar to 9% of the previously reported energy released during substorms. Plain Language Summary The Earth’s near-space environment is populated by energetic charged particles, whose motion is largely controlled by the global geomagnetic field. This region, known as the magnetosphere, is highly dynamic and variable, strongly coupled to the solar wind (a continuous stream of charged particles outflowing from the Sun). At times, the Earth’s magnetic field can become highly distorted and release a large amount of energy into the magnetospheric system. This process is termed a substorm, and the release of energy has significant consequences for the structure of the region and the characteristics of the plasma within it. The amount of energy that is transferred to the magnetospheric particle population remains to be fully understood. In this study, we use spacecraft measurements of highly energetic particles observed by the Van Allen Probes between 2012 and 2017. Using a statistical approach, we quantify the magnitude of the energy input into the particle population due to a typical substorm. Furthermore, we investigate the location of the energy enhancements, providing an insight into how energy is transported throughout the magnetospheric system.last_img read more

Helping heal survivors

first_imgFor nearly 30 years, Dr. Richard F. Mollica has been helping people cope with the worst catastrophes imaginable. The longtime director of the Harvard Program in Refugee Trauma at Massachusetts General Hospital has worked with survivors of the brutal Pol Pot regime in Cambodia, 9/11 in New York, and, most recently, the earthquake in Haiti. Despite witnessing so much tragedy – or perhaps because of it – Dr. Mollica is an optimistic man. He has watched people recover from torture, loss of family members, and, what he considers the worst possible tragedy: the disappearance of loved ones. Like you, he feels empathy for the people of Haiti – but he doesn’t want you to feel too much.http://www.boston.com/news/health/articles/2010/03/01/dr_richard_f_mollica_focuses_on_psychology_following_disaster/last_img read more

In the swim of things

first_img Little swimmers Amanda Garparino tries some strokes for instructor Courtney Otto ’15. One-on-one Courtney Otto ’15 gives one-on-one lessons to Jacy Hoffman. Looking up Helen Colbert, 8, listens to the advice of her instructor, Clare Foster ’13. Kickin’ it Daniel Sickenberger, 8, of West Brookfield, practices with a kickboard. School’s in session The Swim School is an instructional program for ages five and up, including adults, and is run by Harvard coaching staff and taught by the men’s and women’s varsity swimming and diving teams. Diving in Blake Sundel ’15 illustrates proper diving form to his young charges. Immersed David Evans ’61 (left) and Dan Paulsen get some pointers. center_img How good does the prospect of visiting Puerto Rico sound in the middle of January? Or Hawaii? That’s where the Harvard men’s and women’s swimming and diving teams traveled, respectively, this winter. It wasn’t exactly a vacation, but their annual training trip — funded with the money they raise working as instructors in the Harvard Swim School.“The Swim School has been operating since the mid-’70s when former swimming and diving coaches decided it would be a good way to make money and help pay for training trips” by offering lessons to the community, said assistant diving coach Keith Miller, who has helped to oversee the program since arriving at Harvard in 1991.“Our athletes work really hard during the school year. They have morning practices, afternoon practices here … six days a week, which they work around their school schedules. But then during January break, we get to go on a trip someplace where we can really focus on training, get a lot of team bonding, and get a lot of work done in preparation for the big meets at the end of the season.”The school runs twice a year for six weeks, once in the spring, with lessons taught by freshmen and juniors, and once in the fall, taught by sophomores and seniors. “The vast majority of our students are 5 years old through 15 years old, but we also have adults. We probably have 15 or 20 adults each session,” said Miller. Offerings range from beginning nonswimmer instruction to advanced technique, and the school is open to the community.“One of the things I love most about participating in Harvard Swim School is that it bridges a gap between the Harvard undergraduate population and the Cambridge community at large,” said swimmer and co-captain Kristi Korsberg ’12.“Each year, when Harvard students have about five weeks off between fall and spring semesters, the swim and dive team remains on campus to practice,” she said. “Luckily for us, it also means that we have the opportunity to relocate ourselves to a warm climate for a week in the middle of winter. Our goal is simple: to do nothing but focus on quality training without any distractions. These training trips are crucial to our team’s success.”“Puerto Rico was beautiful,” said swimmer and co-captain Matthew McLean ’12. “It’s great to be able to train outdoors, especially during the winter, as it’s a much-needed change to the dreary weather Cambridge provides during that time. We have a bunch of traditions that we carry out, and we always have a meet against another team in Puerto Rico. On an afternoon off, we went to the beach and relaxed. It was great.”Swim students receive top-notch instruction, like that from Olympic qualifier Mike Mosca ’15, a diver. “Mosca is an Ivy League champ this year; he’s excellent,” said Miller. “And I like to have the divers demonstrate on the final day. The kids love that.”But instructing the community has benefits for the swimmers and divers, too.“In a way, it makes us think about our stroke and focus on technique, more so than we would while doing a set in practice. It’s great to have a few hours a week to look at technique and the fundamentals that we learned so long ago, and do it through teaching others,” said McLean.“Verbalizing and explaining particular aspects of stroke technique or justifying why that technique is valuable has enhanced my understanding of swimming,” said Korsberg. “It’s really proved to me that there’s always something to be learned, no matter how much personal experience I think I have.”“I love teaching something that we’re good at, and it feels awesome to have these kids look up to us,” added McLean.For these outgoing seniors, their character has been strengthened through years of instructing, and lifelong memories have been made on the resulting jaunts to St. Croix and Barbados, where the teams have previously gone. There’s dinner with the team every night, followed by activities as a group, and, of course, snorkeling ventures.“In the hotels, we live with multiple other members of the team for an extended amount of time. This always forges friendships that didn’t exist prior to January. So many team memories are made during this time, which is why I already look back on the experiences so fondly,” said Korsberg. “Training trip is without a doubt one of the most important aspects of our season, and it would not be possible without Swim School.” Drying off Matt Karle ’15 (left) and Courtney Otto ’15 conclude a class as Jacy Hoffman of Belmont gets toweled off by her mother, Jing (right). Swimmingly Adult swim Slava Chereukhin (from left), Dan Paulsen, and David Evans ’61 prepare to begin their class. Jon Chase/Harvard Staff Photographerlast_img read more