Browsing by Subject "TAIL"

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  • Juusola, Liisa; Pfau-Kempf, Yann; Ganse, Urs; Battarbee, Markus; Brito, Thiago; Grandin, Maxime; Turc, Lucile; Palmroth, Minna (2018)
    The origin of the flapping motions of the current sheet in the Earth's magnetotail is one of the most interesting questions of magnetospheric dynamics yet to be solved. We have used a polar plane simulation from the global hybrid-Vlasov model Vlasiator to study the characteristics and source of current sheet flapping in the center of the magnetotail. The characteristics of the simulated signatures agree with observations reported in the literature. The flapping is initiated by a hemispherically asymmetric magnetopause perturbation, created by subsolar magnetopause reconnection, that is capable of displacing the tail current sheet from its nominal position. The current sheet displacement propagates downtail at the same pace as the driving magnetopause perturbation. The initial current sheet displacement launches a standing magnetosonic wave within the tail resonance cavity. The travel time of the wave within the local cavity determines the period of the subsequent flapping signatures. Compression of the tail lobes due to added flux affects the cross-sectional width of the resonance cavity as well as the magnetosonic speed within the cavity. These in turn modify the wave travel time and flapping period. The compression of the resonance cavity may also provide additional energy to the standing wave, which may lead to strengthening of the flapping signature. It may be possible that the suggested mechanism could act as a source of kink-like waves that have been observed to be emitted from the center of the tail and to propagate toward the dawn and dusk flanks.
  • Valros, Anna; Sali, Virpi; Hälli, Outi; Saari, Sini; Heinonen, Mari (2021)
    Damaging behaviour, especially tail and ear biting, are common problems in modern pig production. It has been suggested that a low birth weight could predispose pigs to become tail biters. Further, previous studies have shown somewhat contradictory links between growth rate and damaging behaviours, as well as resulting lesions. The aim of this study was to investigate, under practical farm conditions, if birth weight and growth of pigs are related to the risk for damaging behaviours and their outcomes, namely tail and ear lesions. A total of 386 pigs were followed from birth until the end of finishing period on four commercial farm pairs (piglet-producing and finishing farms). Based on birth weight, pigs were categorised as Small and Others, and pigs were weighed around weaning and in the growing and finishing units. At the two latter phases, they were scored for lesions and observed for pig- and environment-directed manipulative behaviour (PMB and EMB, respectively). PMB was not more common in Small than in Other pigs. However, PMB in the growing unit was positively associated with growth rate during suckling and growing periods (p = 0.04 and 0.05, respectively) and EMB was reduced in pigs with high growth rate (p = 0.02) in the finishing unit. Additionally, ear lesions in the growing unit were related to high growth rate in both the suckling (p = 0.03) and the growing period (p < 0.01). The current study shows no evidence that low birth weight predisposes to become a performer of damaging behaviours. Instead, a high growth rate in the suckling and growing period increased the risk for a high level of pig-directed manipulation as well as for becoming a victim of damaging behaviour in the growing unit. We suggest that this could be a consequence of increased feeding motivation in fast-growing pigs: they might experience more competition for feed, and consequently a higher level of stress, which predisposes to damaging behaviour.
  • Brito, Thiago V.; Morley, Steven K. (2017)
    A method for comparing and optimizing the accuracy of empirical magnetic field models using in situ magnetic field measurements is presented. The optimization method minimizes a cost function-tau-that explicitly includes both a magnitude and an angular term. A time span of 21 days, including periods of mild and intense geomagnetic activity, was used for this analysis. A comparison between five magnetic field models (T96, T01S, T02, TS04, and TS07) widely used by the community demonstrated that the T02 model was, on average, the most accurate when driven by the standard model input parameters. The optimization procedure, performed in all models except TS07, generally improved the results when compared to unoptimized versions of the models. Additionally, using more satellites in the optimization procedure produces more accurate results. This procedure reduces the number of large errors in the model, that is, it reduces the number of outliers in the error distribution. The TS04 model shows the most accurate results after the optimization in terms of both the magnitude and direction, when using at least six satellites in the fitting. It gave a smaller error than its unoptimized counterpart 57.3% of the time and outperformed the best unoptimized model (T02) 56.2% of the time. Its median percentage error in vertical bar B vertical bar was reduced from 4.54% to 3.84%. The difference among the models analyzed, when compared in terms of the median of the error distributions, is not very large. However, the unoptimized models can have very large errors, which are much reduced after the optimization. Plain Language Summary We present a method for comparing and optimizing the accuracy of commonly used empirical models that reproduce the Earth's magnetic field for altitudes ranging from a thousand to hundreds of thousands of kilometers. This method uses magnetic field data from satellites orbiting the planet to create a "penalty function" and uses an optimization algorithm to minimize this function and find the model input parameters that produce the best results for a given date and time. Our results show that these models can be improved by the use of satellite data. The model known as TS04 produced the best results after the optimization procedure generating a smaller error in 57.3% of the points in our data set when compared to the standard (unoptimized) inputs. The optimized TS04 also outperformed the best unoptimized model by 56.2%. The differences among all the models analyzed are usually not very large; however, the unoptimized models can have very large errors, which are much reduced by the optimization.
  • Liu, C.M.; Vaivads, A.; Graham, D.B.; Khotyaintsev, Yu V.; Fu, H.S.; Johlander, A.; André, M.; Giles, B.L. (2019)
    Electrostatic solitary waves (ESWs) have been reported inside reconnection jets, but their source and role remain unclear hitherto. Here we present the first observational evidence of ESWs generation by cold ion beams inside the jet, by using high-cadence measurements from the Magnetospheric Multiscale spacecraft in the Earth's magnetotail. Inside the jet, intense ESWs with amplitude up to 30 mV m(-1) and potential up to similar to 7% of the electron temperature are observed in association with accelerated cold ion beams. Instability analysis shows that the ion beams are unstable, providing free energy for the ESWs. The waves are observed to thermalize the beams, thus providing a new channel for ion heating inside the jet. Our study suggests that electrostatic turbulence can play an important role in the jet dynamics.
  • Honkonen, I.; Palmroth, M.; Pulkkinen, T. I.; Janhunen, P.; Aikio, A. (2011)
  • Telkanranta, Helena; Valros, Anna (2020)
    In barren environments of commercial farms, pig often redirect their rooting and chewing behaviours at other pigs, which can lead to tail biting. When materials such as straw are provided, the quantity is usually too small to have an effect. The aim of this study was to test whether small provisions of straw and species-relevant point- source objects would have an additive effect in reducing pen-mate manipulation. The animals were 167 gilts with undocked tails on a commercial farm in Finland, housed in 12-m2 pens with partly slatted floors, on average 7 pigs/pen. Liquid feed and 20 g/pig of long straw were provided once a day. The pigs had continuous access to suspended objects: in each control pen (N =12), a 40cm ×10cm ×2 cm piece of commercially sourced wooden board and a 60-cm metal chain, and in each experimental pen (N =12), an 80-cm piece and two 40-cm pieces of birch trees with a diameter of 5–7 cm, harvested 1 month earlier. After 2 months of exposure, frequencies of pig- and object-directed manipulation before and after consuming the feed and straw were recorded by continuous observation on video. Pre-consumption pig-directed manipulation did not differ between the treatments (means: 39.3 events/pig/hour (SD =11.7) in the experimental pens and 42.1 events/pig/hour (SD =12.1) in the control pens; t =-0.6, df =21, P >0.1), but post-consumption manipulation was significantly lower in frequency in the experimental treatment (means: 31.5 events/pig/hour (SD =10.4) in the experimental pens and 41.0 events/ pig/hour (SD =8.6) in the control pens; t =2.4, df =21, P <0.05). Object-directed manipulation was higher in the experimental treatment both pre- and post-consumption (pre-consumption medians: 9.7 events/pig/hour (min =2.0, max =14.9) in the experimental pens and 3.1 events/pig/hour (min =0.9, max =13.7) in the control pens (U =18.5, P <0.01); post-consumption means: 9.2 events/hour/pig (SD =2.7) in the experimental pens and 4.8 events/pig/hour (SD =2.0) in the control pens (t =4.5, df =20, P <0.001). It was concluded that the experimental objects with improved material, quantity, shape and location had an additive effect with straw in reducing pen-mate manipulation, whereas objects ordinarily used on the farm had no beneficial effect. Further research is needed on the effects of the odour, taste and consistency of optimal objects.