Monday, August 27, 2007

Additions to the pile: Week of 27 August 2007

A slowdown due to summer vacations? Only one GRL in the last week, and three JGRs in the last two weeks.

Kuritsyn, A., H. Ji, S. P. Gerhardt, Y. Ren, and M. Yamada (2007), Effects of global boundary and local collisionality on magnetic reconnection in a laboratory plasma, GRL 34, L16106.

Hollweg, J. V., and P. A. Isenberg (2007), Reflection of Alfvén waves in the corona and solar wind: An impulse function approach, JGR 112, A08102.

Gosling, J. T., S. Eriksson, D. J. McComas, T. D. Phan, and R. M. Skoug (2007), Multiple magnetic reconnection sites associated with a coronal mass ejection in the solar wind, JGR 112, A08106.

Frederick-Frost, K. M., K. A. Lynch, P. M. Kintner, E. Klatt, D. Lorentzen, J. Moen, Y. Ogawa, and M. Widholm (2007), SERSIO: Swalbard EISCAT rocket study of ion outflows, JGR 112, A08307.

Tuesday, August 21, 2007

Off to Berkeley

I'm headed to a science working team meeting at UC Berkeley for the FAST satellite, and I'll be gone the rest of the week.

Additions to the pile: Week of 20 August 2007

AGU's website was getting hammered yesterday, so I only checked GRL.

Bortnik, J., R. M. Thorne, N. P. Meredith, and O. Santolik (2007), Ray tracing of penetrating chorus and its implications for the radiation belts, GRL 34, L15109.

Gosling, J. T., T. D. Phan, R. P. Lin, and A. Szabo (2007), Prevalence of magnetic reconnection at small field shear angles in the solar wind, GRL 34, L15110.

Vennerstrom, S., F. Christiansen, N. Olsen, and T. Moretto (2007), On the cause of IMF By related mid- and low latitude magnetic disturbances, GRL 34, L16101.

Tuesday, August 14, 2007

I do not think that word means what you think it means

As reported in the Financial Times:
"We were seeing things that were 25-standard deviation moves, several days in a row,” said David Viniar, Goldman’s chief financial officer.

By Chebyshev's inequality, no matter what the probability distribution, the fraction of points which lie within k standard deviations of the mean must be at least (1 - 1/k2). For a normal (Gaussian) distribution, the probability of a 25 standard deviation outlier is much less, so much so as to be negligible. But even for the less stringent bound, the probability of being 25 or more standard deviations from the mean is at most 1/625, or 0.0016. To do that for three days in a row is at most (1/625)3 = 1/244140625 = 4.096 * 10-9.

Put another way: There are about 250 trading days in a year (weekdays, excluding holidays). Even at the Chebyshev limit, it would take an expected million years or so to get three straight days of 25 standard deviation outliers. And Viniar's comment does not rule out a longer run of outliers.

Either these guys have botched the calculation, or they do not understand what standard deviation actually means.

(h/t Brad DeLong)

Monday, August 13, 2007

R.I.P. R. A. Alpher

Ralph A. Alpher, the last surviving author of the paper by Alpher, Bethe, and Gamow, has passed away.

(h/t Uncertain Principles)

Additions to the pile: Weeks of 6 August and 13 August 2007

Articles of interest in the last two weeks:

Sitnov, M. I., P. N. Guzdar, and M. Swisdak (2007), Atypical durrent sheets and plasma bubbles: A self-consistent kinetic model, GRL 34, L15101.

Trávníček, P., P. Hellinger, M. G. G. T. Taylor, C. P. Escoubet, I. Dandouras, and E. Lucek (2007), Magnetosheath plasma expansion: Hybrid simulations, GRL 34, L15104.

Hubert, B., K. Kauristie, O. Amm, S. E. Milan, A. Grocott, S. W. H. Cowley, and T. I. Pulkkinen (2007), Auroral streamers and magnetic flux closure, GRL 34, L15105.

Bahcivan, H. (2007), Plasma wave heating during extreme electric fields in the high latitude E region, GRL 34, L15106.

Watanabe, M., A. Kadokura, N. Sato, and T. Saemundsson (2007), Absence of geomagnetic conjugacy in pulsating auroras, GRL 34, L15107. At 7 pages, longer than some JGR papers.

Villante, U., P. Francia, M. Vellante, P. Di Giuseppe, A. Nubile, and M. Piersanti (2007), Correction to "Long-period oscillations at discrete frequencies: A comparative analysis of ground, magnetospheric , and interplanetary observations," JGR 112, A08202. The original paper is JGR 112, A04210.

Fairfield, D. H., M. M. Kuznetsova, T. Mukai, T. Nagai, T. I. Gombosi, and A. J. Ridley (2007), Waves on the dusk flank boundary layer during very northward interplanetary magnetic field conditions: Observations and simulation, JGR 112, A08206.

Trattner, K. J., J. S. Mulcock, S. M. Petrinec, and S. A. Fuselier (2007), Probing the boundary between antiparallel and component reconnection during southward interplanetary magnetic field conditions, JGR 112, A08210.